Why am I getting this error?
public class ParameterParser
{
public List<string> ParseParameter(string queryString)
{
queryString = queryString.Replace(" ", "");
string[] strs = queryString.Split(#"(", #"=", #",", #"<>",
StringSplitOptions.None);
List<string> parameters = new List<string>();
foreach (string ss in strs)
{
string s = ss.Trim(')');
if (s.StartsWith("#") && !s.Equals("") && s!=null)
{
parameters.Add(s.Replace(" ", ""));
}
}
return parameters;
}
}
Error 3 The best overloaded method match for 'string.Split(params char[])' has some invalid arguments F:...\ParameterParser.cs
If you want to pass an array of strings, you have to do that explicitly:
string[] strs = queryString.Split(new string[] {"(", "=", ",", "<>"},
StringSplitOptions.None);
I suspect you were modelling your code on something like this:
string[] strs = queryString.Split('(', '=', ',');
This is using a parameter array (the params modifier in C#). Parameter arrays are only applicable for the final parameter, and no overload of String.Split takes a params string[]. That's why it wasn't working for you.
Note that I've changed the strings into simple string literals - I would recommend only using verbatim string literals when you actually need to.
#"(", #"=", #",", #"<>" is not a single string or a char[] array
Try this:
string[] strs = queryString.Split(new string[] {#"(", #"=",#",",#"<>" },StringSplitOptions.None);
Related
I’m trying to get the variable name instead of the value to pass it to another method
eg.
String myString = "xyz";
String getVariableName(String s){
// What i want is if the above string is passed [getVariableName(myString)]
//i want it to return ['myString']
}
This is generally not possible. At best, if there are a finite number of String variables you care about, you could manually make a collection of them, and then search it:
final stringVariables = <String, String Function()>{
'myString': () => myString,
'myOtherString': () => myOtherString,
};
var myString = 'xyz';
var myOtherString = 'abc';
String getVariableName(String s) {
for (var entry in stringVariables.entries) {
if (entry.value() == s) {
return entry.key;
}
}
return '';
}
void main() {
print(getVariableName('xyz')); // Prints: myString
myString = 'foo';
print(getVariableName('foo')); // Prints: myString
}
Note that stringVariables's above must use a Function as a thunk to delay evaluation of the variable; otherwise the variable name would be associated with whatever value it happened to have when stringVariables is first accessed and wouldn't work if your variables are reassigned.
All that said, I don't really recommend doing any of this. This sounds like an XY problem. You should be asking about whatever it is you ultimately want to do, and there probably is a better way to accomplish that task.
I wrote this code to convert dynamic list to Word list but linter says:
Omit type annotations for local variables. on 2nd line.
However if I omit type annotations, I get an error A value of type 'List<dynamic>' can't be returned from method 'convert' because it has a return type of 'List<Word>'.
It there any smarter way to convert?
static List<Word> convert(List<dynamic> words) {
final List<Word> wordsList = [];
words.forEach((v) {
final map = Map<String, dynamic>.from(v as Map<dynamic, dynamic>);
wordsList.add(Word.fromMap(map));
});
return wordsList;
}
Word.fromMap is:
Word.fromMap(Map<String, dynamic> map)
: text = map['text'] as String,
count = map['count'] as int;
To avoid the warning, and put the type on the right-hand side as the lint wants, just write:
final wordsList = <Word>[];
I assume words is JSON data, so the maps are already Map<String, dynamic>. Then you can also do everything in one line:
static List<Word> convert(List<dynamic> words) =>
[for (var v in words) Word.fromMap(v)];
Use the cast() method like this:
class Word {
final String text;
final int count;
static List<Word> convert(List<dynamic> words) {
final List<Word> wordsList = [];
words.cast<Map<dynamic, dynamic>>().forEach((v) { // <-- look here
final map = Map<String, dynamic>.from(v);
wordsList.add(Word.fromMap(map));
});
return wordsList;
}
Word.fromMap(Map<String, dynamic> map)
: text = map['text'] as String,
count = map['count'] as int;
}
It will ensure the casting are done on each element. Make sure the type are correct since it will else result in a type-cast error.
Is there a generic way to retrieve PropertyInfo based on a string value alone, when deeper than one level.
I assume this is probably simple enough, but my search results are only as good as my search criteria, and I think I am having an issue articulating the proper keywords to get search results for what I am after.
I would like to be able to do something like the following (which works perfect if the key is for a direct property / one level - ie key = 'firstName'):
public static PropertyInfo (this HtmlHelper htmlHelper, string key) {
PropertyInfo pInfo = htmlHelper.ViewData.Model.GetType().GetProperty(key);
return pInfo;
}
But is there a way for me to return the PropertyInfo based on a string alone
when Key equals something more complex, such as nested classes, objects, lists, etc...:
key = "somelist[0].myproperty"
key = "Items[0].someotherlist[1].someproperty" (where Items is defined as List<Item> Items {get; set;}, someotherlist is defined similarly)
Can the method be generic enough to essentially drill down as many levels as needed (defined)?
So here is what I came up with... this is about to get wordy, and mostly 'stream of thought'
I have custom HtmlHelperExtension, and within it :
PropertyInfo[] pInfoArray = htmlHelper.ViewData.Model.GetType().GetProperties();
PropertyInfo pInfo = GetPropertyInfo(pInfoArray, key);
This GetPropertyInfo() method takes the key, and the PropertyInfo array, cycles through the properties, until the keypart (using regex to remove any indication of an array from the string, so I am left with only the property) matches the property name. On Match, determine if this is the first cycle in the loop, and if so assign the matched property to my Temp Type and PropertyInfo variables. If keyParts are remaining to loop through, subsequent loops now use previously set temp variables and the for loop index [i] to iterate / drill down the class structure. Each time setting the pInfoTemp variable, and then pTypeTemp so the next loop can use where it left off.
private static PropertyInfo GetPropertyInfo(PropertyInfo[] pInfoArray, string key)
{
PropertyInfo pInfo = null;
string[] keyParts = key.Split('.');
Regex arrayRgx = new Regex("\\[\\d*\\]");
PropertyInfo pInfoTemp = null;
Type pTypeTemp = null;
foreach (PropertyInfo prop in pInfoArray)
{
string keyPartsTrimmed = arrayRgx.Replace(keyParts[0], ""); // removes '[#]' from string
if (keyPartsTrimmed == prop.Name) // match property name
{
for (int i = 0; i < keyParts.Count(); i++)
{
if (i == 0) // initial item [0]
{
pTypeTemp = prop.PropertyType; // gets [0]'s type
pInfoTemp = prop; // assigns [0]'s property info
}
else
{
pInfoTemp = GetNestedPropertyInfo(pTypeTemp, arrayRgx.Replace(keyParts[i], "")); // gets [i]'s property info for return or next iteration
pTypeTemp = pInfoTemp.PropertyType; // gets [i]'s type for next iteration
}
}
pInfo = pInfoTemp;
break;
}
}
return pInfo;
}
This next method is invoked by the previous for grabbing nested property info, more importantly for detecting whether the passedItemType is a List (without this, it fails to work correctly as it is unable to find the property asked for in a List<> Type. I need to know what the List item Type is.
private static PropertyInfo GetNestedPropertyInfo(Type passedItemType, string passedProperty)
{
PropertyInfo pInfoOut = null;
if (passedItemType.IsGenericType && passedItemType.GetGenericTypeDefinition() == typeof(List<>))
{
Type itemType = passedItemType.GetGenericArguments()[0];
pInfoOut = itemType.GetProperty(passedProperty);
}
else
{
pInfoOut = passedItemType.GetProperty(passedProperty);
}
return pInfoOut;
}
This currently suits my requirements as they are today, and I have tested it with the following properties, lists, subclasses, subclasses with lists, etc.. to 4 levels deep, but should function properly no matter the depth:
firstName
lastName
Items[1].sprocket
subClass.subClassInt
subClass.mySubClassObj.sprocketObj
subClass.ItemsInMySubClass[1].sprocket
subClass.ItemsInMySubClass[0].mySubClassObj.widgetObj
subClass.ItemsInMySubClass[2].mySubClassObj.sprocketObj
If anyone has a better solution, or see any potential issues with what I have, I welcome the feedback.
The best way in your case is to make a parser that split that expression.
I'm writing an ASP.NET MVC 3 site and I need to convert some integer values from the database that represent statuses with user readable strings, for example:
...
<td>
#item.Status
</td>
...
I've written an HTML Helper to do the conversion:
public static string MessageType(this HtmlHelper helper, int type)
{
string messageType = "Unknown";
switch((Types.MessageTypes)type)
{
case Types.MessageTypes.Join:
messageType = "Join App";
break;
case Types.MessageTypes.New:
messageType = "New App";
break;
}
return messageType;
}
And I'm storing the types as an enumeration in the Types class.
My question is whether there is a cleaner way to do this? I don't like these magic strings in my code and it creates numerous dependencies in different parts of the code.
Any thoughts?
Many thanks,
Sam
I usual decorate the enums with the DisplayAttribute like this.
enum MessageTypes
{
[Display(Name = "Join App")]
Join,
[Display(Name = "New App")]
New
}
Then I use a helper to extract them:
public static string EnumDisplay(this HtmlHelper helper, Enum model)
{
var enumType = model.GetType();
var modelValue = Convert.ToInt64(model);
var matches = from field in enumType.GetMembers()
where field.MemberType == MemberTypes.Field && Enum.IsDefined(enumType, field.Name)
let value = Convert.ToInt64(Enum.Parse(enumType, field.Name, false))
where modelValue == value
let attribute = field.GetCustomAttributes(typeof (DisplayAttribute), false).Cast<DisplayAttribute>().FirstOrDefault()
select attribute == null
? field.Name
: attribute.Name;
return matches.FirstOrDefault() ?? "Unknown";
}
Then you can do
#Html.EnumDisplay((MessageType)item.MessageType)
In my opinion, you should be storing the corresponding user readable strings in the database next to the integer. And return an object e.g. StatusViewModel to the view model. the View model may have >
class StatusViewModel
{
int type;
string displayMessage;
}
makes sense?
I'm getting this error:
ex = {"The binary operator Equal is not defined for the types 'MySite.Domain.DomainModel.EntityFramework.NickName' and 'System.Int32'."}
What I tried to do was do a select all where the NickNameId = someIntPassedIn... the problem is that the NickNameId is a foreign key, so when it compares the someIntPassedIn to the NickNameId it pulls the whole NickName object that the NickNameId refers to and tries to compare the int to that object.
I need a solution here to allow it to compare the int to the NickName object's Id... so
A) How can I define the binary operator Equal for comparing these two objects
OR
B) How can I compare it directly to the id instead of the whole object?
You don't have to read this, but here's the SelectAllByKey method incase it helps: (I passed in "NickNameId" and "1")
public IList<E> SelectAllByKey(string columnName, string key)
{
KeyProperty = columnName;
int id;
Expression rightExpr = null;
if (int.TryParse(key, out id))
{
rightExpr = Expression.Constant(id);
}
else
{
rightExpr = Expression.Constant(key);
}
// First we define the parameter that we are going to use the clause.
var xParam = Expression.Parameter(typeof(E), typeof(E).Name);
MemberExpression leftExpr = MemberExpression.Property(xParam, this._KeyProperty);
int temp;
BinaryExpression binaryExpr = MemberExpression.Equal(leftExpr, rightExpr);
//Create Lambda Expression for the selection
Expression<Func<E, bool>> lambdaExpr = Expression.Lambda<Func<E, bool>>(binaryExpr, new ParameterExpression[] { xParam });
//Searching ....
IList<E> resultCollection = ((IRepository<E, C>)this).SelectAll(new Specification<E>(lambdaExpr));
if (null != resultCollection && resultCollection.Count() > 0)
{
//return valid single result
return resultCollection;
}//end if
return null;
}
Let me know if you need any more info.
Thanks,
Matt
You should call SelectAllByKey('NickName.ID','1').
Since ID is property of property, you could use this extension method:
public static MemberExpression PropertyOfProperty(this Expression expr,string propertyName)
{
var properties = propertyName.Split('.');
MemberExpression expression = null;
foreach (var property in properties)
{
if (expression == null)
expression = Expression.Property(expr, property);
else
expression = Expression.Property(expression, property);
}
return expression;
}
The accepted answer seems way too complicated for the problem at hand, if I'm reading this correctly.
If I understand you correctly, you're trying to run a query like:
var q = from e in Context.SomeEntities
where e.NickNameId == someIntPassedIn
select e;
...but this won't work, because e.NickNameId is an entity, not an integer.
To reference the Id property, you can just refer to it, like this:
var q = from e in Context.SomeEntities
where e.NickNameId.Id == someIntPassedIn
select e;
Update: If you can't use strong-typed properties due to your level of abstraction (per your comment), then use query builder methods:
var q = (ObjectQuery<T>)Repository.SelectSomething();
return q.Where("it.NickName.Id = " + someIntPassedIn.ToString());
You can adapt this as you see fit, but the general point is that the EF already knows how to translate strings to property members.