C# Generics and Type Checking

c# generics types

Jon · Jun 11, 2009 · Viewed 130.4k times · Source

I have a method that uses an IList<T> as a parameter. I need to check what the type of that T object is and do something based on it. I was trying to use the T value, but the compiler does not not allow it. My solution is the following:

private static string BuildClause<T>(IList<T> clause)
{
    if (clause.Count > 0)
    {
        if (clause[0] is int || clause[0] is decimal)
        {
           //do something
        }
        else if (clause[0] is String)
        {
           //do something else
        }
        else if (...) //etc for all the types
        else
        {
           throw new ApplicationException("Invalid type");
        }
    } 
}

There has to be a better way to do this. Is there some way I can check the type of T that is passed in and then use a switch statement?

Answer

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)){...}

C# Generics and Type Checking

Answer

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