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Give the example code below, can anyone explain why the first typeof() call works successfully but the second fails?? It doesn't matter if they are classes or interfaces it fails either way.
interface ITestOne<T1>
{
T1 MyMethod();
}
interface ITestMany<T1, T2>
{
T1 MyMethod(T2 myParameter);
}
void Main()
{
var typeOne = typeof(ITestOne<>); //This line works
var typeTwo = typeof(ITestMany<>); //Compile error
}
445
It is prohibited that a type implements or extends two different instantiations of the same interface. This is because the bridge method generation process cannot handle this situation.
Java Generic Interface In similar way, we can create generic interfaces in java. We can also have multiple type parameters as in Map interface. Again we can provide parameterized value to a parameterized type also, for example new HashMap<String, List<String>>(); is valid.
You can declare variant generic interfaces by using the in and out keywords for generic type parameters. ref , in , and out parameters in C# cannot be variant. Value types also do not support variance. You can declare a generic type parameter covariant by using the out keyword.
The general syntax to declare a generic interface is as follows: interface interface-name<T> { void method-name(T t); // public abstract method. } In the above syntax, <T> is called a generic type parameter that specifies any data type used in the interface.
You need to let the compiler know that you're looking for the generic type with two generic arguments. Add a comma between the angle brackets:
var typeTwo = typeof(ITestMany<,>);
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