CODEWITHSUNDEEP
c#dictionarycasting
whoami
whoami

Reputation: 1899

casting error when casting a list of object to a dictionary of enum as key and list of objects as value

I have enum/classes as follows

public enum TestType
{
    Automatic,
    Manual,
    SemiManual,
    SemiAutomatic
}

public class TestCase
{
    public int Id { get; set; }

}

public class TestData
{
    public TestType TestType { get; set; }
    public int Id { get; set; }
}

Its used as follows

static void Main(string[] args)
{
    List<TestData> data = new List<TestData>()
    {
        new TestData(){ TestType = TestType.Automatic, Id = 21 },
        new TestData(){ TestType = TestType.SemiAutomatic, Id = 34 },
        new TestData(){ TestType = TestType.SemiManual, Id = 13 },
        new TestData(){ TestType = TestType.Manual, Id = 14 },
        new TestData(){ TestType = TestType.Automatic, Id = 45 },
        new TestData(){ TestType = TestType.Automatic, Id = 56 }
    };


}

I need to convert this list into a Dictionary<TestType, List<TestCase>>. For that I have code as follows.

Dictionary<TestType, List<TestCase>> dataAsDictionary =
                        data.GroupBy(x => x.TestType)
                        .ToDictionary(k => k.Key, v => v.Select( f=> 
                                new TestCase() { Id = f.Id }));

Error CS0029 Cannot implicitly convert type 'System.Collections.Generic.Dictionary<ConsoleApp2.TestType, System.Collections.Generic.IEnumerable<ConsoleApp2.TestCase>>' to 'System.Collections.Generic.Dictionary<ConsoleApp2.TestType, System.Collections.Generic.List<ConsoleApp2.TestCase>>' ConsoleApp2

How can I resolve this error? I try various combinations of casting but that doesn't seem to help

Upvotes: 2

Views: 76

Answers (2)

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726539

You get this error because Select() returns IEnumerable<T>, while your Dictionary wants values of type List<T>.

Add a call of ToList() to fix this problem:

Dictionary<TestType,List<TestCase>> dataAsDictionary = data
    .GroupBy(x => x.TestType)
    .ToDictionary(
        k => k.Key
    ,   v => v.Select( f=> new TestCase() { Id = f.Id }).ToList()
    ); //                                               ^^^^^^^^^

Upvotes: 2

MarcinJuraszek
MarcinJuraszek

Reputation: 125620

Add a ToList call:

Dictionary<TestType, List<TestCase>> dataAsDictionary =
                        data.GroupBy(x => x.TestType)
                        .ToDictionary(k => k.Key, v => v.Select( f=> 
                                new TestCase() { Id = f.Id }).ToList());

It's needed because Select returns IEnumerable<T> and not List<T>.

Upvotes: 2

Related Questions