C# Generics and Type Checking

You could use overloads:

public static string BuildClause(List<string> l){...}

public static string BuildClause(List<int> l){...}

public static string BuildClause<T>(List<T> l){...}

Or you could inspect the type of the generic parameter:

Type listType = typeof(T);
if(listType == typeof(int)){...}

You can use typeof(T).

private static string BuildClause<T>(IList<T> clause)
{
     Type itemType = typeof(T);
     if(itemType == typeof(int) || itemType == typeof(decimal))
    ...
}

By default know there is not a great way. Awhile back I got frustrated with this and wrote a little utility class that helped out a bit and made the syntax a bit cleaner. Essentially it turns the code into

TypeSwitcher.Do(clause[0],
  TypeSwitch.Case<int>(x => ...),  // x is an int
  TypeSwitch.Case<decimal>(d => ...), // d is a decimal 
  TypeSwitch.Case<string>(s => ...)); // s is a string

Full blog post and details on the implementation are available here

• http://blogs.msdn.com/jaredpar/archive/2008/05/16/switching-on-types.aspx