判断参数是不是泛型的方法C#

原文：https://learn.microsoft.com/en-us/dotnet/framework/reflection-and-codedom/how-to-examine-and-instantiate-generic-types-with-reflection

Constructing an Instance of a Generic Type

A generic type is like a template. You cannot create instances of it unless you specify real types for its generic type parameters. To do this at run time, using reflection, requires the MakeGenericType method.

To construct an instance of a generic type

Get a Type object that represents the generic type. The following code gets the generic type Dictionary<TKey,TValue> in two different ways: by using the Type.GetType(String) method overload with a string describing the type, and by calling the GetGenericTypeDefinition method on the constructed type Dictionary\<String, Example> (Dictionary(Of String, Example) in Visual Basic). The MakeGenericType method requires a generic type definition.

// Use the typeof operator to create the generic type
// definition directly. To specify the generic type definition,
// omit the type arguments but retain the comma that separates
// them.
Type d1 = typeof(Dictionary<,>);

// You can also obtain the generic type definition from a
// constructed class. In this case, the constructed class
// is a dictionary of Example objects, with String keys.
Dictionary<string, Example> d2 = new Dictionary<string, Example>();
// Get a Type object that represents the constructed type,
// and from that get the generic type definition. The
// variables d1 and d4 contain the same type.
Type d3 = d2.GetType();
Type d4 = d3.GetGenericTypeDefinition();