Radio Button List not being generated from identical code - asp.net-mvc

I am currently pulling my hair out. I have an ASP.NET MVC web site with two forms, both have radio buttons on them. On the first page (that works), the radio list appears just fine. However, on the second page the radio buttons are not even present in the source code. Here is the code chunk from the first page (BestTimeType is an Enum that I made):
//Back End
[DisplayName("Time:")]
public RadioButtonListViewModel<BestTimeType> BestTimeRadioList { get; set; }
public EvalModel()
{
BestTimeRadioList = new RadioButtonListViewModel<BestTimeType>
{
Id = "BestTime",
SelectedValue = BestTimeType.Afternoon,
ListItems = new List<RadioButtonListItem<BestTimeType>>
{
new RadioButtonListItem<BestTimeType>{Text = "Morning", Value = BestTimeType.Morning},
new RadioButtonListItem<BestTimeType>{Text = "Afternoon", Value = BestTimeType.Afternoon},
new RadioButtonListItem<BestTimeType>{Text = "Evening", Value = BestTimeType.Evening}
}
};
}
// Front End
<div class="grid_1 evalLabel reqField" style="padding-top: 5px;">
<%= Html.LabelFor(model => model.BestTimeRadioList)%>
</div>
<div class="grid_4" style="text-align: center; padding: 5px 0px 10px 0px;">
<%= Html.RadioButtonListFor(model => model.BestTimeRadioList) %>
</div>
Here is the code chunk for the second page:
//Back End
[Required(ErrorMessage = "*")]
[DisplayName("HS Diploma:")]
public RadioButtonListViewModel<bool> HsDiplomaRadioList { get; set; }
public EmploymentModel()
{
HsDiplomaRadioList = new RadioButtonListViewModel<bool>
{
Id = "HsDiploma",
SelectedValue = false,
ListItems = new List<RadioButtonListItem<bool>>
{
new RadioButtonListItem<bool> {Text = "Yes", Value = true},
new RadioButtonListItem<bool> {Text = "No", Value = false}
}
};
}
//Front End
<div class="grid_2 employLabel reqField">
<%= Html.LabelFor(model => model.HsDiplomaRadioList) %>
</div>
<div class="grid_3">
<%= Html.RadioButtonListFor(model => model.HsDiplomaRadioList)%>
<%= Html.ValidationMessageFor(model => model.HsDiplomaRadioList)%>
</div>
I also tried making a custom Enum for the HsDiplomaRadioList (Yes/No), but the radio did not show up either.
I must be missing something extremely stupid simple. If any more code is necessary, I will be glad to put them up.
Thanks in advance.
Edit
Here is the code for RadioButtonList:
public static class HtmlHelperExtensions
{
public static string RadioButtonListFor<TModel, TRadioButtonListValue>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, RadioButtonListViewModel<TRadioButtonListValue>>> expression) where TModel : class
{
return htmlHelper.RadioButtonListFor(expression, null);
}
public static string RadioButtonListFor<TModel, TRadioButtonListValue>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, RadioButtonListViewModel<TRadioButtonListValue>>> expression, object htmlAttributes) where TModel : class
{
return htmlHelper.RadioButtonListFor(expression, new RouteValueDictionary(htmlAttributes));
}
public static string RadioButtonListFor<TModel, TRadioButtonListValue>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, RadioButtonListViewModel<TRadioButtonListValue>>> expression, IDictionary<string, object> htmlAttributes) where TModel : class
{
var inputName = GetInputName(expression);
RadioButtonListViewModel<TRadioButtonListValue> radioButtonList = GetValue(htmlHelper, expression);
if (radioButtonList == null)
return String.Empty;
if (radioButtonList.ListItems == null)
return String.Empty;
var divTag = new TagBuilder("div");
divTag.MergeAttribute("id", inputName);
divTag.MergeAttribute("class", "radio");
foreach (var item in radioButtonList.ListItems)
{
var radioButtonTag = RadioButton(htmlHelper, inputName, new SelectListItem { Text = item.Text, Selected = item.Selected, Value = item.Value.ToString() }, htmlAttributes);
divTag.InnerHtml += radioButtonTag;
}
return string.Concat(divTag, htmlHelper.ValidationMessage(inputName, "*"));
}
public static string GetInputName<TModel, TProperty>(Expression<Func<TModel, TProperty>> expression)
{
if (expression.Body.NodeType == ExpressionType.Call)
{
var methodCallExpression = (MethodCallExpression)expression.Body;
string name = GetInputName(methodCallExpression);
return name.Substring(expression.Parameters[0].Name.Length + 1);
}
return expression.Body.ToString().Substring(expression.Parameters[0].Name.Length + 1);
}
private static string GetInputName(MethodCallExpression expression)
{
// p => p.Foo.Bar().Baz.ToString() => p.Foo OR throw...
var methodCallExpression = expression.Object as MethodCallExpression;
if (methodCallExpression != null)
{
return GetInputName(methodCallExpression);
}
return expression.Object.ToString();
}
public static string RadioButton(this HtmlHelper htmlHelper, string name, SelectListItem listItem,
IDictionary<string, object> htmlAttributes)
{
var inputIdSb = new StringBuilder();
inputIdSb.Append(name)
.Append("_")
.Append(listItem.Value);
var sb = new StringBuilder();
var builder = new TagBuilder("input");
if (listItem.Selected) builder.MergeAttribute("checked", "checked");
builder.MergeAttribute("type", "radio");
builder.MergeAttribute("value", listItem.Value);
builder.MergeAttribute("id", inputIdSb.ToString());
builder.MergeAttribute("name", name + ".SelectedValue");
builder.MergeAttributes(htmlAttributes);
sb.Append(builder.ToString(TagRenderMode.SelfClosing));
sb.Append(RadioButtonLabel(inputIdSb.ToString(), listItem.Text, htmlAttributes));
//sb.Append("<br>");
return sb.ToString();
}
public static string RadioButtonLabel(string inputId, string displayText,
IDictionary<string, object> htmlAttributes)
{
var labelBuilder = new TagBuilder("label");
labelBuilder.MergeAttribute("for", inputId);
labelBuilder.MergeAttributes(htmlAttributes);
labelBuilder.InnerHtml = displayText;
return labelBuilder.ToString(TagRenderMode.Normal);
}
public static TProperty GetValue<TModel, TProperty>(HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression) where TModel : class
{
TModel model = htmlHelper.ViewData.Model;
if (model == null)
{
return default(TProperty);
}
Func<TModel, TProperty> func = expression.Compile();
return func(model);
}
}
Ok finally got around to stack tracing (I should do this first, but I was in a rush last night) and found that for some reason model.HsDiplomaRadio is null. I will need to track down the cause of this.

Related

Custom DropDownListFor Helper loads an empty value for the selected element

I am using a custom helper, to create a select element that can take HtmlAttribute. I am using the same code as I found here, in #Alexander Puchkov answer (which I'll post for reference).
It's working fine, apart when the DDL helper is loaded with one of the option as the selected item, then the value of the selected item is null/empty. (i.e. on an edit page the DDL loads up with the option that was set on creation, rather than the '-Please select option-'),
The highlighted attribute in the picture shows the problem, the value should not be empty, but should show 'Medium'...
So the text is display correctly but the element has no value. Any ideas on where this issue comes from?
Here is the full code of the helper:
/// <summary>
/// A selectListItem with an extra property to hold HtmlAttributes
/// <para>Used in conjunction with the sdDDL Helpers</para>
/// </summary>
public class SdSelectListItem : SelectListItem
{
public object HtmlAttributes { get; set; }
}
/// <summary>
/// Generate DropDownLists with the possibility of styling the 'option' tags of the generated 'select' tag
/// </summary>
public static class SdDdlHelper
{
public static MvcHtmlString sdDDLFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper,
Expression<Func<TModel, TProperty>> expression, IEnumerable<SdSelectListItem> selectList,
string optionLabel, object htmlAttributes)
{
if (expression == null)
throw new ArgumentNullException("expression");
ModelMetadata metadata = ModelMetadata.FromLambdaExpression<TModel, TProperty>(expression, htmlHelper.ViewData);
return SelectInternal(htmlHelper, metadata, optionLabel, ExpressionHelper.GetExpressionText(expression), selectList,
false /* allowMultiple */, HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes));
}
public static MvcHtmlString sdDDLFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper,
Expression<Func<TModel, TProperty>> expression, IEnumerable<SdSelectListItem> selectList,
object htmlAttributes)
{
if (expression == null)
throw new ArgumentNullException("expression");
ModelMetadata metadata = ModelMetadata.FromLambdaExpression<TModel, TProperty>(expression, htmlHelper.ViewData);
//-> The below line is my problem (specifically the 'null' param), it set to null if no option label is passed to the method...So if I use this overload, the DDL will load (or re-load) with the default value selected, not the value binded to the property - And if I use the above overload, and set Model.action_priority as the optionLabel, then I get what is shown in the picture...
return SelectInternal(htmlHelper, metadata, null, ExpressionHelper.GetExpressionText(expression), selectList,
false /* allowMultiple */, HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes));
}
#region internal/private methods
private static MvcHtmlString SelectInternal(this HtmlHelper htmlHelper, ModelMetadata metadata, string optionLabel, string name,
IEnumerable<SdSelectListItem> selectList, bool allowMultiple,
IDictionary<string, object> htmlAttributes)
{
string fullName = htmlHelper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(name);
if (String.IsNullOrEmpty(fullName))
throw new ArgumentException("No name");
if (selectList == null)
throw new ArgumentException("No selectlist");
object defaultValue = (allowMultiple)
? htmlHelper.GetModelStateValue(fullName, typeof(string[]))
: htmlHelper.GetModelStateValue(fullName, typeof(string));
// If we haven't already used ViewData to get the entire list of items then we need to
// use the ViewData-supplied value before using the parameter-supplied value.
if (defaultValue == null)
defaultValue = htmlHelper.ViewData.Eval(fullName);
if (defaultValue != null)
{
IEnumerable defaultValues = (allowMultiple) ? defaultValue as IEnumerable : new[] { defaultValue };
IEnumerable<string> values = from object value in defaultValues
select Convert.ToString(value, CultureInfo.CurrentCulture);
HashSet<string> selectedValues = new HashSet<string>(values, StringComparer.OrdinalIgnoreCase);
List<SdSelectListItem> newSelectList = new List<SdSelectListItem>();
foreach (SdSelectListItem item in selectList)
{
item.Selected = (item.Value != null)
? selectedValues.Contains(item.Value)
: selectedValues.Contains(item.Text);
newSelectList.Add(item);
}
selectList = newSelectList;
}
// Convert each ListItem to an <option> tag
StringBuilder listItemBuilder = new StringBuilder();
// Make optionLabel the first item that gets rendered.
if (optionLabel != null)
listItemBuilder.Append(
ListItemToOption(new SdSelectListItem()
{
Text = optionLabel,
Value = String.Empty,
Selected = false
}));
foreach (SdSelectListItem item in selectList)
{
listItemBuilder.Append(ListItemToOption(item));
}
TagBuilder tagBuilder = new TagBuilder("select")
{
InnerHtml = listItemBuilder.ToString()
};
tagBuilder.MergeAttributes(htmlAttributes);
tagBuilder.MergeAttribute("name", fullName, true /* replaceExisting */);
tagBuilder.GenerateId(fullName);
if (allowMultiple)
tagBuilder.MergeAttribute("multiple", "multiple");
// If there are any errors for a named field, we add the css attribute.
System.Web.Mvc.ModelState modelState;
if (htmlHelper.ViewData.ModelState.TryGetValue(fullName, out modelState))
{
if (modelState.Errors.Count > 0)
{
tagBuilder.AddCssClass(HtmlHelper.ValidationInputCssClassName);
}
}
tagBuilder.MergeAttributes(htmlHelper.GetUnobtrusiveValidationAttributes(fullName, metadata));
return MvcHtmlString.Create(tagBuilder.ToString(TagRenderMode.Normal));
}
internal static string ListItemToOption(SdSelectListItem item)
{
TagBuilder builder = new TagBuilder("option")
{
InnerHtml = HttpUtility.HtmlEncode(item.Text)
};
if (item.Value != null)
{
builder.Attributes["value"] = item.Value;
}
if (item.Selected)
{
builder.Attributes["selected"] = "selected";
}
builder.MergeAttributes(HtmlHelper.AnonymousObjectToHtmlAttributes(item.HtmlAttributes));
return builder.ToString(TagRenderMode.Normal);
}
internal static object GetModelStateValue(this HtmlHelper htmlHelper, string key, Type destinationType)
{
System.Web.Mvc.ModelState modelState;
if (htmlHelper.ViewData.ModelState.TryGetValue(key, out modelState))
{
if (modelState.Value != null)
{
return modelState.Value.ConvertTo(destinationType, null /* culture */);
}
}
return null;
}
#endregion
}
}
Here is how I call it in the View (using Razor):
#Html.sdDDLFor(x => Model.action_priority, Model.actionPriorityDDL(), Model.action_priority, new
{
#id = "_Action_Priority_DDL",
#class = "form-control"
})
And finally here is the Model.actionPriorityDDL() method:
public List<SdSelectListItem> actionPriorityDDL()
{
action_priority_DDL = new List<SdSelectListItem>();
action_priority_DDL.Add(new SdSelectListItem
{
Value = StringRepository.ActionPriority.high,
Text = StringRepository.ActionPriority.high,
HtmlAttributes = new
{
#class = "lbl-action-priority-high"
}
}
);
action_priority_DDL.Add(new SdSelectListItem
{
Value = StringRepository.ActionPriority.medium,
Text = StringRepository.ActionPriority.medium,
HtmlAttributes = new
{
#class = "lbl-action-priority-medium"
}
}
);
action_priority_DDL.Add(new SdSelectListItem
{
Value = StringRepository.ActionPriority.low,
Text = StringRepository.ActionPriority.low,
HtmlAttributes = new
{
#class = "lbl-action-priority-low"
}
}
);
action_priority_DDL.Add(new SdSelectListItem
{
Value = StringRepository.ActionPriority.psar,
Text = StringRepository.ActionPriority.psar,
HtmlAttributes = new
{
#class = "lbl-action-priority-psar"
}
}
);
return action_priority_DDL;
}
This is caused by a former bug in MVC framework (http://aspnet.codeplex.com/workitem/8311; accessible here: https://web.archive.org/web/20131208041521/http://aspnet.codeplex.com/workitem/8311) that happens when using the DropDownListFor helper within a loop, i.e. the model property has an indexer (like in your example, where the generated select element has an attribute name="actionList[0].action_priority")
I resolved this by copying some code from here https://github.com/ASP-NET-MVC/aspnetwebstack/blob/master/src/System.Web.Mvc/Html/SelectExtensions.cs
Specifically, in this method
private static MvcHtmlString SelectInternal(this HtmlHelper htmlHelper, ModelMetadata metadata, string optionLabel, string name,
IEnumerable<ExtendedSelectListItem> selectList, bool allowMultiple,
IDictionary<string, object> htmlAttributes)
replace this
if (selectList == null)
throw new ArgumentException("No selectlist");
with:
bool usedViewData = false;
// If we got a null selectList, try to use ViewData to get the list of items.
if (selectList == null)
{
selectList = htmlHelper.GetSelectData(name);
usedViewData = true;
}
Now, replace this
if (defaultValue == null)
defaultValue = htmlHelper.ViewData.Eval(fullName);
with:
if (defaultValue == null && !String.IsNullOrEmpty(name))
{
if (!usedViewData)
{
defaultValue = htmlHelper.ViewData.Eval(name);
}
else if (metadata != null)
{
defaultValue = metadata.Model;
}
}
Finally, you also need to add this method:
private static IEnumerable<SelectListItem> GetSelectData(this HtmlHelper htmlHelper, string name)
{
object o = null;
if (htmlHelper.ViewData != null)
{
o = htmlHelper.ViewData.Eval(name);
}
if (o == null)
{
throw new InvalidOperationException(
String.Format(
CultureInfo.CurrentCulture,
MvcResources.HtmlHelper_MissingSelectData,
name,
"IEnumerable<SelectListItem>"));
}
IEnumerable<SelectListItem> selectList = o as IEnumerable<SelectListItem>;
if (selectList == null)
{
throw new InvalidOperationException(
String.Format(
CultureInfo.CurrentCulture,
MvcResources.HtmlHelper_WrongSelectDataType,
name,
o.GetType().FullName,
"IEnumerable<SelectListItem>"));
}
return selectList;
}
replacing SelectListItem with your custom class (e.g. SdSelectListItem, or ExtendedSelectListItem , or whatever you named it )

How to Use check box list in MVC

I need to display check box list with more than one options. User must select minimum one check box, user can select more than one check boxes.
I want to store values of all check boxes (selected) in one field as a string(Data base) with coma separated. This is not mandatory, mandatory is need to store multiple values of each selected check box. Alternate solutions are welcome.
Model
public class Member
{
public string Member_VehicalType { get; set; }
public IList<SelectListItem> Member_VehicalType_List { get; set; }
Controller
[HttpGet]
public ActionResult Create()
{
Member objMemberModel = new Member();
List<SelectListItem> vehical_Types = new List<SelectListItem>();
vehical_Types.Add(new SelectListItem { Text = "Two Wheeler", Value = "1" });
vehical_Types.Add(new SelectListItem { Text = "Four Wheeler", Value = "2" });
objMemberModel.Member_VehicalType_List = vehical_Types;
return View(objMemberModel);
How do I create view with #Html.CheckBoxFor( or #Html.CheckBox(
I recently had to deal with SelectListItem as a checkbox-list. I came up with the following HtmlExtensions, which might be helpful. These extensions provide the same functionality as the #Html.DropDownListFor(model => ...);
Usage: #Html.CheckBoxListFor(model => model.ModelMemberToPutValueIn, Model.Member_VehicalType_List)
public static class HtmlExtensions
{
public static MvcHtmlString CheckBoxListFor<TModel, TValue>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TValue>> expression, IEnumerable<SelectListItem> items, object htmlAttributes = null)
{
var listName = ExpressionHelper.GetExpressionText(expression);
var metaData = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
items = GetCheckboxListWithDefaultValues(metaData.Model, items);
return htmlHelper.CheckBoxList(listName, items, htmlAttributes);
}
public static MvcHtmlString CheckBoxList(this HtmlHelper htmlHelper, string listName, IEnumerable<SelectListItem> items, object htmlAttributes = null)
{
if (items == null) return null;
var container = new TagBuilder("div");
container.AddCssClass("checkbox-list");
container.MergeAttribute("id", HtmlHelper.GenerateIdFromName(listName));
foreach (var item in items)
{
var id = HtmlHelper.GenerateIdFromName(String.Join(".", listName, item.Text));
var div = new TagBuilder("div");
div.AddCssClass("checkbox");
var cb = new TagBuilder("input");
cb.MergeAttribute("type", "checkbox");
cb.MergeAttribute("id", id);
cb.MergeAttribute("name", listName);
cb.MergeAttribute("value", item.Value ?? item.Text);
if (item.Selected) cb.MergeAttribute("checked", "checked");
var label = new TagBuilder("label");
label.MergeAttribute("for", id);
label.MergeAttributes(new RouteValueDictionary(htmlAttributes), true);
label.InnerHtml = item.Text;
div.InnerHtml = cb.ToString(TagRenderMode.SelfClosing) + label;
container.InnerHtml += div;
}
return new MvcHtmlString(container.ToString());
}
private static IEnumerable<SelectListItem> GetCheckboxListWithDefaultValues(object defaultValues, IEnumerable<SelectListItem> selectList)
{
var defaultValuesList = defaultValues as IEnumerable;
if (defaultValuesList == null) return selectList;
var values = from object value in defaultValuesList select Convert.ToString(value, CultureInfo.CurrentCulture);
var selectedValues = new HashSet<string>(values, StringComparer.OrdinalIgnoreCase);
var newSelectList = new List<SelectListItem>();
foreach (var item in selectList)
{
item.Selected = (item.Value != null) ? selectedValues.Contains(item.Value) : selectedValues.Contains(item.Text);
newSelectList.Add(item);
}
return newSelectList;
}
}

DropDownListFor for enum with custom values (stored in attributes) doesn't select item

I have enum with assigned string values (in attributes) and would like to have html helper for displaying it. Unfortunately I need to use assigned values as a keys in ddl. Because of that it doesn't select item stored in ViewModel. What to do?
Sample Enum
public enum StatusEnum
{
[Value("AA")]
Active,
[Value("BB")]
Disabled
}
ViewModel
public class UserViewModel
{
public StatusEnum Status { get; set; }
}
View
#Html.DropDownListForEnum(x => x.Status, new {})
DropDownListForEnum helper
public static MvcHtmlString DropDownListForEnum<TModel, TEnum>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TEnum>> expression, object htmlAttributes)
{
var metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
IEnumerable<SelectListItem> items = Enum.GetNames(typeof(TEnum))
.Select(n => (TEnum)Enum.Parse(typeof(TEnum), n))
.Select(e => new SelectListItem() {
Text = e.ToString(),
Value = EnumExtension.GetValue(e).ToString(),
Selected = EnumExtension.GetValue(e) == EnumExtension.GetValue(metadata.Model)
})
.ToList();
return htmlHelper.DropDownListFor(expression, items, htmlAttributes);
}
Instead of passing IEnumerable<SelectListItem> to the dropdown, create and populate SelectList manually and pass that and it will work:
public static MvcHtmlString DropDownListForEnum<TModel, TEnum>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TEnum>> expression, object htmlAttributes)
{
var metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
var items = Enum.GetNames(typeof(TEnum))
.Select(n => (TEnum)Enum.Parse(typeof(TEnum), n))
.Select(e => new
{
Id = Convert.ToInt32(e),
Text = e.ToString(),
Value = EnumExtension.GetValue(e).ToString(),
Selected = EnumExtension.GetValue(e) == EnumExtension.GetValue(metadata.Model)
})
.ToList();
var selectList = new SelectList(items, "Text", "Value", selectedValue: items.Find(i => i.Selected).Text);
return htmlHelper.DropDownListFor(expression, selectList, htmlAttributes);
}

MVC 3 CheckboxList and me...Part 3. Try specifying the type arguments explicitly

This IS fun.
Ok, I have the following model(s):
public class My : BusinessCategory
{
[Display(Name = "What types of energy do you use?")]
public List<MyTypes> MyTypeList { get; set; }
public bool? FirstOption { get; set; }
public bool? SecondOption{ get; set; }
public bool? ThirdOption{ get; set; }
public bool? FourthOption { get; set; }
}
Where MyTypes:
public class MyTypes
{
public int MyTypeId { get; set; }
public string MyTypeName { get; set; }
public bool? MyTypeValue { get; set; }
}
My controller is as follows:
public ActionResult My(Guid id)
{
try
{
var model = Model(id);
SetMyTypeList(model.My);
ViewBag.MyTypeMe = new MultiSelectList(model.My.MyTypeList, "MyTypeValue", "MyTypeName");
return View(model.My);
}
catch (Exception ex)
{
ExceptionHelper.WriteLog(ex);
return RedirectToAction("Error");
}
}
private void SetMyTypeList(My model)
{
model.MyTypeList = new List<MyTypes>();
model.MyTypeList.Add(new MyTypes { MyTypeId = 1, MyTypeName = GetName.GetDisplayName(model, m => m.FirstOption), MyTypeValue = model.FirstOption });
model.MyTypeList.Add(new MyTypes { MyTypeId = 2, MyTypeName = GetName.GetDisplayName(model, m => m.SecondOption), MyTypeValue = model.SecondOption});
model.MyTypeList.Add(new MyTypes { MyTypeId = 3, MyTypeName = GetName.GetDisplayName(model, m => m.ThirdOption), MyTypeValue = model.ThirdOption});
model.MyTypeList.Add(new MyTypes { MyTypeId = 4, MyTypeName = GetName.GetDisplayName(model, m => m.FourthOption), MyTypeValue = model.FourthOption });
}
public static string GetDisplayName<TModel, TProperty>(TModel model, Expression<Func<TModel, TProperty>> expression)
{
return ModelMetadata.FromLambdaExpression<TModel, TProperty>(expression, new ViewDataDictionary<TModel>(model)).DisplayName;
}
And finally the view is as follows:
#model Valpak.Websites.HealthChecker.Models.My
#{
ViewBag.Title = "My";
}
<h2>
My</h2>
#using (Html.BeginForm())
{
#Html.ValidationSummary(true)
<fieldset>
<legend>My Management</legend>
<div style="text-align: left; padding-left: 47%;">
#Html.ListBoxFor(model => model.MyTypeList, ViewBag.MyTypeMe as MultiSelectList)
#Html.CheckBoxListFor(model => model.MyTypeList, ViewBag.EnergyTypeMe as MultiSelectList, Model.ReviewId)
</div>
<p>
<input type="submit" value="Continue" />
</p>
</fieldset>
}
<div>
#Html.ActionLink("Cancel and return to categories", "BusinessSummary", new { id = Model.ReviewId })
</div>
CheckboxListFor, if it was working, would use the following extension:
public static class HtmlHelper
{
//Extension
public static MvcHtmlString CheckBoxListFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty[]>> expression, MultiSelectList multiSelectList, object htmlAttributes = null)
{
//Derive property name for checkbox name
MemberExpression body = expression.Body as MemberExpression;
string propertyName = body.Member.Name;
//Get currently select values from the ViewData model
TProperty[] list = expression.Compile().Invoke(htmlHelper.ViewData.Model);
//Convert selected value list to a List<string> for easy manipulation
List<string> selectedValues = new List<string>();
if (list != null)
{
selectedValues = new List<TProperty>(list).ConvertAll<string>(delegate(TProperty i) { return i.ToString(); });
}
//Create div
TagBuilder divTag = new TagBuilder("div");
divTag.MergeAttributes(new RouteValueDictionary(htmlAttributes), true);
//Add checkboxes
foreach (SelectListItem item in multiSelectList)
{
divTag.InnerHtml += String.Format("<div><input type=\"checkbox\" name=\"{0}\" id=\"{0}_{1}\" " +
"value=\"{1}\" {2} /><label for=\"{0}_{1}\">{3}</label></div>",
propertyName,
item.Value,
selectedValues.Contains(item.Value) ? "checked=\"checked\"" : "",
item.Text);
}
return MvcHtmlString.Create(divTag.ToString());
}
}
Can someone you explain in very simplistic terms (I’m a bit dense) why I can use the ListBoxFor example but this dies and gives me the following error when I use the checkbox?
CS0411: The type arguments for method 'Extensions.HtmlHelper.CheckBoxListFor<TModel,TProperty>(System.Web.Mvc.HtmlHelper<TModel>, System.Linq.Expressions.Expression<System.Func<TModel,TProperty[]>>, System.Web.Mvc.MultiSelectList, System.Guid, object)' cannot be inferred from the usage. Try specifying the type arguments explicitly.
Can anyone offer any sort of work around as I’d quite like to use my :’(
As always, apologies for my ignorance.
In the signature of the extension method you have the following second argument:
Expression<Func<TModel, TProperty[]>> expression,
This basically means that the expression must return an array of TProperty => TProperty[]
whereas in your view model you have a List<T>:
public List<MyTypes> EnergyTypeList { get; set; }
and inside your view you are using:
model => model.EnergyTypeList
Your code doesn't work because List<EnergyTypeList> is not the same thing as EnergyTypeList[].
So you have different possibilities. Either change the type in your view model to match the one in your helper or use change your helper to use a List or even better an IEnumerable<TProperty>. This way the extension method will work even with arrays.

solution to the asp.net mvc drop down list selected value overrider problem

I wrote a helper method to display enums from my model in my asp.net MVC application as drop down lists in my views.
Here is my code for that:
public static List<SelectListItem> CreateSelectItemList<TEnum>(object enumObj,
string defaultItemKey,
bool sortAlphabetically,
object firstValueOverride)
where TEnum : struct
{
var values = (from v in (TEnum[])Enum.GetValues(typeof(TEnum))
select new
{
Id = Convert.ToInt32(v),
Name = ResourceHelpers.GetResourceValue(AppConstants.EnumResourceNamespace,
typeof(TEnum).Name, v.ToString())
});
return values.ToSelectList(e => e.Name,
e => e.Id.ToString(),
!string.IsNullOrEmpty(defaultItemKey) ? ResourceHelpers.GetResourceValue(AppConstants.EnumResourceNamespace, defaultItemKey) : string.Empty,
enumObj,
sortAlphabetically,
firstValueOverride);
}
This actually generates the select item list:
public static List<SelectListItem> ToSelectList<T>(
this IEnumerable<T> enumerable,
Func<T, string> text,
Func<T, string> value,
string defaultOption,
object selectedVal,
bool sortAlphabetically,
object FirstValueOverride)
{
int iSelectedVal = -1;
if(selectedVal!=null)
{
try
{
iSelectedVal = Convert.ToInt32(selectedVal);
}
catch
{
}
}
var items = enumerable.Select(f => new SelectListItem()
{
Text = text(f),
Value = value(f),
Selected = (iSelectedVal > -1)? (iSelectedVal.ToString().Equals(value(f))) : false
});
#region Sortare alfabetica
if (sortAlphabetically)
items = items.OrderBy(t => t.Text);
#endregion Sortare alfabetica
var itemsList = items.ToList();
Func<SelectListItem, bool> funct = null;
string sValue = string.Empty;
SelectListItem firstItem = null;
SelectListItem overridenItem = null;
int overridenIndex = 0;
if (FirstValueOverride != null)
{
sValue = FirstValueOverride.ToString();
funct = (t => t.Value == sValue);
overridenItem = itemsList.SingleOrDefault(funct);
overridenIndex = itemsList.IndexOf(overridenItem);
if (overridenItem != null)
{
firstItem = itemsList.ElementAt(0);
itemsList[0] = overridenItem;
itemsList[overridenIndex] = firstItem;
}
}
if(!string.IsNullOrEmpty(defaultOption))
itemsList.Insert(0, new SelectListItem()
{
Text = defaultOption,
Value = "-1"
});
return itemsList;
}
These is the method I call:
public static MvcHtmlString EnumDropDownList<TEnum>(this HtmlHelper htmlHelper,
object enumObj,
string name,
string defaultItemKey,
bool sortAlphabetically,
object firstValueOverride,
object htmlAttributes)
where TEnum : struct
{
return htmlHelper.DropDownList(name,
CreateSelectItemList<TEnum>(enumObj,
defaultItemKey,
sortAlphabetically,
firstValueOverride),
htmlAttributes);
}
Now I am having the problem described here
When I call this helper method and the input's name is the same as the property's name the selected value doesn't get selected.
The alternate solution described there doesn't work for me. The only solution that works is changing the name and not using the model binding using FormCollection instead.
I don't like this workaround because I can't use validation any more using the ViewModel pattern and I have to write some extra code for every enum.
I tried writing a custom model binder to compensate for this somehow but none of the methods I can override there gets called when I start the action.
Is there any way to do this without using FormCollection?
Can I somehow intercept ASP.NET MVC when it tries to put the value into my input field and make it select the right value?
Thank you in advance.
I have a sollution now
Here is the code for the EnumDropDownList function the other functions are listed in the question:
public static MvcHtmlString EnumDropDownList(this HtmlHelper htmlHelper,
object enumObj,
string name,
string defaultItemKey,
bool sortAlphabetically,
object firstValueOverride,
object htmlAttributes)
{
StringBuilder sbRezultat = new StringBuilder();
int selectedIndex = 0;
var selectItemList = new List<SelectListItem>();
if (enumObj != null)
{
selectItemList = CreateSelectItemList(enumObj, defaultItemKey, true, null);
var selectedItem = selectItemList.SingleOrDefault(item => item.Selected);
if (selectedItem != null)
{
selectedIndex = selectItemList.IndexOf(selectedItem);
}
}
var dict = HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes);
TagBuilder tagBuilder = new TagBuilder("select");
tagBuilder.MergeAttribute("name", name,true);
bool bReadOnly = false;
//special case for readonly
if(dict.ContainsKey("readonly"))
{
//remove this tag it won't work the way mvc renders it anyway
dict.Remove("readonly");
bReadOnly = true;
}
//in case the style element is completed if the drop down is not readonly
tagBuilder.MergeAttributes(dict, true);
if (bReadOnly)
{
//add a small javascript to make it readonly and add the lightgrey style
tagBuilder.MergeAttribute("onchange", "this.selectedIndex=" + selectedIndex + ";",true);
tagBuilder.MergeAttribute("style", "background: lightgrey", true);
}
sbRezultat.Append(tagBuilder.ToString(TagRenderMode.StartTag));
foreach (var option in selectItemList)
{
sbRezultat.Append(" <option value='");
sbRezultat.Append(option.Value);
sbRezultat.Append("' ");
if (option.Selected)
sbRezultat.Append("selected");
sbRezultat.Append(" >");
sbRezultat.Append(option.Text);
sbRezultat.Append("</option>");
}
sbRezultat.Append("</select>");
return new MvcHtmlString(sbRezultat.ToString());
}
I also wrote a generic function of type For (EnumDropDownFor):
public static MvcHtmlString EnumDropDownListFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper,
Expression<Func<TModel, TProperty>> expression,
string defaultItemKey,
bool sortAlphabetically,
object firstValueOverride,
object htmlAttributes)
where TProperty : struct
{
string inputName = GetInputName(expression);
object selectedVal = null;
try
{
selectedVal = htmlHelper.ViewData.Model == null
? default(TProperty)
: expression.Compile()(htmlHelper.ViewData.Model);
}
catch//in caz ca e ceva null sau ceva de genu'
{
}
return EnumDropDownList(htmlHelper,
selectedVal,
inputName,
defaultItemKey,
sortAlphabetically,
firstValueOverride,
htmlAttributes);
}
and some helper methods:
public static string GetInputName<TModel, TProperty>(Expression<Func<TModel, TProperty>> expression)
{
if (expression.Body.NodeType == ExpressionType.Call)
{
MethodCallExpression methodCallExpression = (MethodCallExpression)expression.Body;
string name = GetInputName(methodCallExpression);
return name.Substring(expression.Parameters[0].Name.Length + 1);
}
return expression.Body.ToString().Substring(expression.Parameters[0].Name.Length + 1);
}
private static string GetInputName(MethodCallExpression expression)
{
MethodCallExpression methodCallExpression = expression.Object as MethodCallExpression;
if (methodCallExpression != null)
{
return GetInputName(methodCallExpression);
}
return expression.Object.ToString();
}

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