When I use this linq I am getting error
The model item passed into the dictionary is of type 'System.Linq.Enumerable+WhereSelectEnumerableIterator'2[System.Char,System.Char]', but this dictionary requires a model item of type 'System.Collections.Generic.IEnumerable`1[groupBylinq.Models.employee]'.
This is my action
public ActionResult Index()
{
var result = from n in db.employees.Where(x => x.gender=="female")
.GroupBy(x => x.employee_sno).ToList() select n;
return View(result);
}
Result of GroupBy method is structure like [grouping_key, array[employee]]. But your view expect an array of employees. To achieve this you can do next
return View(result.SelectMany(v=>v).ToList());
But are you sure that you need GroupBy operator?
Related
I have this query below and it returns a
IQueryable<IEnumerable<YogaSpaceEvent>>
but I want tit to return a List of YogaSpaceEvents
var listYogaEvents = dbContext.YogaProfiles.Select(i => i.YogaSpaceEvents.Where(j => j.EventStatus == YogaSpaceEventStatus.Active));
How do I get it to return a
List<YogaSpaceEvents>
Change the Select to SelectMany then call ToList like this:
List<YogaSpaceEvents> result =
dbContext.YogaProfiles
.SelectMany(i => i.YogaSpaceEvents.Where(j =>
j.EventStatus == YogaSpaceEventStatus.Active)).ToList();
This will collapse (flatten) all the nested IEnumerable<YogaSpaceEvent> and then accumulate the elements into a List instance.
Below is the code in question. I receive Object reference not set to an instance of an object. on the where clause inside the Linq query. However, this only happens after it goes through and builds my viewpage.
Meaning: If I step through using debugger, I can watch it pull the correct order I am filtering for, go to the correct ViewPage, fill in the model/table with the correct filtered item, and THEN it comes back to my Controller and shows me the error.
public ActionResult OrderIndex(string searchBy, string search)
{
var orders = repositoryOrder.GetOpenOrderList();
if (Request.QueryString["FilterOrderNumber"] != null)
{
var ordersFiltered = from n in orders
where n.OrderNumber.ToUpper().Contains(Request.QueryString["FilterOrderNumber"].ToUpper().ToString())
select n;
return View(ordersFiltered);
}
return View(orders);
}
its always better to manipulate your strings and other things outside the linq query ,
please refer : http://msdn.microsoft.com/en-us/library/bb738550.aspx
from the readability point of view also its not good ,
public ActionResult OrderIndex(string searchBy, string search)
{
var orders = repositoryOrder.GetOpenOrderList();
var orderNumber = Request.QueryString["FilterOrderNumber"];
if (!string.IsNullOrEmpty(orderNumber))
{
orderNumber = orderNumber.ToUpper();
var ordersFiltered = from n in orders
where n.OrderNumber.ToUpper().Contains(orderNumber)
select n;
return View(ordersFiltered);
}
return View(orders);
}
Your query is not being executed in your Action method because you don't have a ToList (or equivalent) added to your query. When your code returns, your query will be enumerated somewhere in your view and that's the point where the error occurs.
Try adding ToList to your query like this to force query execution in your action method:
var ordersFiltered = (from n in orders
where n.OrderNumber.ToUpper().Contains(Request.QueryString["FilterOrderNumber"].ToUpper().ToString())
select n).ToList();
What's going wrong is that a part of your where clause is null. This could be your query string parameter. Try moving the Request.QueryString part out of your query and into a temporary variable. If that's not the case make sure that your orders have an OrderNumber.
You both were right. Just separately.
This fixed my problem
var ordersFiltered = (from n in orders
where !string.IsNullOrEmpty(n.OrderNumber) && n.OrderNumber.ToUpper().Contains(Request.QueryString["FilterOrderNumber"].ToUpper().ToString())
select n);
This question already has answers here:
Working with C# Anonymous Types
(8 answers)
Closed 8 years ago.
I am using ASP.NET mvc 5. I have one class that holds all the LINQ which can access to another class. now i convert the LINQ query to list variable Query and returning as IList... the i create object of this class--> call the method and get result.
now i can see in debugging object names but i can't see in foreach loop. my list hold mix data types, plus result is merging from different tables...
public IList GetAllFeeZonesForFeeSchemeByID(int FeeSchemeID)
{
using (var db = new QualificationContext())
{
var Query = from a in db.FeeScheme
join b in db.FeeZoneSchema.Where(c => c.FeeSchemeID == 1) on a.FeeSchemeID equals b.FeeSchemeID
join c in db.FeeZone on b.FeeZoneID equals c.FeeZoneID
select new
{
FeeScheme = a.FeeSchemeID,
FeeZone = b.FeeZoneID,
FeeZone_Description = c.FeeZoneDescription
};
return Query.ToList();
}
}
in controller class...
foreach(var item in obj1.GetAllFeeZonesForFeeSchemeByID(1))
{
item.???? (can't access the object here....
}
many thanks
You should return Generic IList of concrete (not anonymous class):
public IList<FeeSchemeModel> GetAllFeeZonesForFeeSchemeByID(int FeeSchemeID)
{
using (var db = new QualificationContext())
{
var Query = from a in db.FeeScheme
join b in db.FeeZoneSchema.Where(c => c.FeeSchemeID == 1) on a.FeeSchemeID equals b.FeeSchemeID
join c in db.FeeZone on b.FeeZoneID equals c.FeeZoneID
select new FeeSchemeModel
{
FeeScheme = a.FeeSchemeID,
FeeZone = b.FeeZoneID,
FeeZone_Description = c.FeeZoneDescription
};
return Query.ToList();
}
}
public class FeeSchemeModel
{
public int FeeScheme{get;set;}
public int FeeZone{get;set;}
public string FeeZone_Description{get;set;}
};
But I recommend to use IEnumerable<T> instead of IList<T> and use ToArray() method instead of ToList() method if you don't use special features of List<T> (such as method Add())
IList is non-generic interface, it contains only non-generic IEnumerable definition, which enumerates objects. So type of item will be object. That's why you can see only members of System.Object class.
You should either cast item to appropriate type or use generic collection parametrized with appropriate type. But you can't use neither of these approaches while you are using anonymous objects, because you don't know anonymous type name. So, you need to create some class which you will be able to cast to:
foreach(Foo item in obj1.GetAllFeeZonesForFeeSchemeByID(1))
Or use as parameter of method return type:
public IList<Foo> GetAllFeeZonesForFeeSchemeByID(int FeeSchemeID)
One more option is usage of dynamic type, which will resolve operations on object at runtime. You still will not be able to use IntelliSense but your code will work:
foreach(dynamic item in obj1.GetAllFeeZonesForFeeSchemeByID(1))
{
// use item.FeeScheme
}
var query = _db.Mst_Users
.Where(item => item.CustomerUserId == customerUserId)
.Traverse(item => _db.Mst_Users.Where(parent => item.CustomerUserId == parent.ParentId))
.Select(item =>Convert.ToString(item.CustomerUserId)).ToArray();
In the above query I'm getting customerUserIds in an array:
int[] ids = query;
From the above int array:
var getgroup = from item in _db.Mst_Group
where ids.Contains(item.CustomerUserId)
select item;
However, it shows the following error:
int[] does not contain a definition for Contains and the best extension method overload system.linq.iqueryable.contains<tsource>
Try ToList() instead of ToArray() in the first query.
It will return a List<int> that contains the "Contains" method
List<int> ids = query;
1) I've a Product table with 4 columns: ProductID, Name, Category, and Price. Here's the regular linq to query this table.
public ActionResult Index()
{
private ProductDataContext db = new ProductDataContext();
var products = from p in db.Products
where p.Category == "Soccer"
select new ProductInfo { Name = p.Name, Price = p.Price}
return View(products);
}
Where ProductInfo is just a class that contains 2 properties (Name and Price). The Index page Inherits ViewPage - IEnumerable - ProductInfo. Everything works fine.
2) To dynamicaly execute the above query, I do this:
Public ActionResult Index()
{
var products =
db.Products
.Where("Category = \"Soccer\"")
.Select(/* WHAT SOULD I WRITE HERE TO SELECT NAME & PRICE?*/)
return View(products);
}
I'm using both 'System.Lind.Dynamic' namespace and the DynamicLibrary.cs (downloaded from ScottGu blog).
Here are my questions:
What expression do I use to select only Name and Price?
(Most importantly) How do I retrieve the data in my view? (i.e. What type the ViewPage inherits? ProductInfo?)
===================
EDIT
When I write .Select("new(Name, Price)"), I'm able to pass an object to the ViewData's Model property. Unfortunately, in order to use the Viewdata object, I'm asked to cast the Viewdata to a type. But, I do not know how to determine the type to do the casting.
====================
EDIT
Instead of the ViewData's Model property, I'm using simply the ViewData["products"]. To retrieve the content, I just place a IEnumerable cast before the ViewData, like this:
<% foreach(var item in (IEnumerable)ViewData["products"]){%>
<p><% = Html.Encode(item)%><p>
<%}%>
There are 2 situations:
1) If I select only one column (for instance, Name), everything work fine.
2) If I select more than 1 more columns (Name, Price), I get something like this
{Name=Soccer, Price=19.50}
{Name=Shin Pads, Price=11.59}
Why I just don't get something like
Soccer, 19.50
Shin Pads, 11.59
=================================
EDIT April 02 - 05h47 AM
I've define the GetPropertyValue Method (as your response suggets) as static in a static Class that I called 'HelperClass'. Now, this is the way I try to access the value of Name from my object.
<% = Html.Encode(HelperClass.GetPropertyValue(ViewData["product"], "Name")) %>
I get the following Exception:"Object reference not set to an instance of an object". And, the following line from the inside GetPropertyValue() his highlight.
Line 22: return propInfo.GetValue(obj, null);
Do I need to use new keyword? (where?)
Thanks for helping
Private Sub filter()
Dim coll = db.Products.Where(Function(x) x.Category.Equals("Soccer")) _
.Select(Function(x) GetObject(x.Name, x.Price))
End Sub
Private Function GetObject(ByVal name As String, ByVal price As String) As Object
Return new ProductInfo(name, price)
End Function
1) To generate a new projection type at runtime you can:
.Select("new(Name, Price)")
2) To read values from the object, you need to use reflection:
string name = GetPropertyValue(someObject, "Name");
...
public static object GetPropertyValue(object obj, string propName)
{
System.Reflection.PropertyInfo propInfo = obj.GetType().GetProperty(propName);
return propInfo.GetValue(obj, null);
}