Using Lambda Expressions trees with IEnumerable
- by Loathian
I've been trying to learn more about using Lamba expression trees and so I created a simple example. Here is the code, this works in LINQPad if pasted in as a C# program.
void Main()
{
IEnumerable<User> list = GetUsers().Where(NameContains("a"));
list.Dump("Users");
}
// Methods
public IEnumerable<User> GetUsers()
{
yield return new User{Name = "andrew"};
yield return new User{Name = "rob"};
yield return new User{Name = "chris"};
yield return new User{Name = "ryan"};
}
public Expression<Func<User, bool>> NameContains(string namePart)
{
return u => u.Name.Contains(namePart);
}
// Classes
public class User
{
public string Name { get; set; }
}
This results in the following error:
The type arguments for method 'System.Linq.Enumerable.Where(System.Collections.Generic.IEnumerable, System.Func)' cannot be inferred from the usage. Try specifying the type arguments explicitly.
However if I just substitute the first line in main with this:
IEnumerable<User> list = GetUsers().Where(u => u.Name.Contains("a"));
It works fine. Can tell me what I'm doing wrong, please?
