Creating a Lambda Contains expression

Question

I want to create a class which wraps a list of structures.

I have the following code:

public struct MyData
{
    public int ID;
    public string Description;
}

public class MyClass
{
    private List<MyData> data;

    public bool Contains(string desc)
    {
        if (data != null)
        {
            return data.Contains(item => item.Description.Contains(desc));
        }

        return false;
    }        
}

I can't see why I'm unable to use a Lambda expression, the error that I get is:

Cannot convert lambda expression to type 'MyApp.MyData' because it is not a delegate type

Answer 1

In your case Contains expects you to pass it a MyData , if you want to use a lambda for comparison then use Any

return data.Any(item => item.Description.Contains(desc)); 

Answer 2

public bool Contains( string desc )
{
    return data != null && data.Exists( item => item.Description.Contains( desc ) );
}

Answer 3

The reason is because the List<T>Contains method expects a T , whereas you've given it a lambda expression, created with the => .

What you could do is:

data.Any(item => item.Description.Contains(desc));