Determining types with generics

The following program outputs "We have something else". How do I properly determine a DataType of the type being passed in?

void Main()
{
    AFunction(typeof(string));
}

void AFunction<T>(T aType) {

    if (aType.GetType() == typeof(string)) {

        Console.WriteLine ("We have a string");

    } else {
开发者_运维知识库        Console.WriteLine ("We have something else");
    }
}

Use the is keyword.

if(aType is string)
    Console.WriteLine("We have a string");
else
    Console.WriteLine("We have something else");

One thing to note when using this kind of logic is that is will return true for super-types which could lead to unexpected behavior:

if(myObj is object)
    Console.WriteLine("This will always print");
else if(myObj is int)
    Console.WriteLine("This will never print");

if you're looking for type from a (small) finite list, you can use 'is'.

I think you don't need to use Generic Type in this circumstance. You just send an Object Type to the AFunction and then use the is keyword as follows:

void AFunction(Object aType) 
{ 
     if (aType is string) { 

        Console.WriteLine ("We have a string"); 

    } else { 
        Console.WriteLine ("We have something else"); 
    } 
} 

By the way, I think that the Generic Type is not for this kind of usage.

typeof(string) returns a Type.

So the compiler infers that you mean to call AFunction<Type>(typeof(string)).

GetType returns a Type that represents the type Type for an instance of Type.

typeof(Type) does not equal typeof(string), so the result is exactly as expected.

Did you mean

AFunction<string>("Hello World");

void AFunction<T>(T value)
{
    if (value is string) ...
}

or

AFunction(typeof(string));

void AFunction(Type type)
{
    if (type == typeof(string)) ...
}

or

AFunction<string>();

void AFunction<T>()
{
    if (typeof(T) == typeof(string)) ...
}

?

Using your current calls you could make AFunction something like this:

void AFunction<T>(T aType)
{
    if ((aType as Type).Name == "String")
    {
        Console.WriteLine("We have a string");
    }
    else
    {
        Console.WriteLine("We have something else");
    }
}