Generic methods have type parameters. They provide a way to parameterize the types used in a method. This means you can provide only one implementation and call it with different types. Generic methods require an unusual syntax form.
Generic Class
Note:The syntax form for the declaration uses the <T> characters after the method name but before the formal parameter list.
Example
This program demonstrates the use of a generic method in the C# language. Generic methods use at least one explicit type parameter, which is customarily the type T or V or TValue or similar.
Also:This type is an open type.
It is not precisely described in the program.
Few assumptions about its representation can be made.
It is not precisely described in the program.
Few assumptions about its representation can be made.
using System;
using System.Collections.Generic;
class Program
{
static List<T> GetInitializedList<T>(T value, int count)
{
// This generic method returns a List with ten elements initialized.
// ... It uses a type parameter.
// ... It uses the "open type" T.
List<T> list = new List<T>();
for (int i = 0; i < count; i++)
{
list.Add(value);
}
return list;
}
static void Main()
{
// Use the generic method.
// ... Specifying the type parameter is optional here.
// ... Then print the results.
List<bool> list1 = GetInitializedList(true, 5);
List<string> list2 = GetInitializedList<string>("Perls", 3);
foreach (bool value in list1)
{
Console.WriteLine(value);
}
foreach (string value in list2)
{
Console.WriteLine(value);
}
}
}
Output
True
True
True
True
True
Perls
Perls
Perls
This program uses a generic method to construct a List with a certain number of elements of a certain type and with a specific initial value. The GetInitializedList member is the generic method and it uses a type parameter with name T.
List Examples
Note:The first parameter to the GetInitializedList method is also a value of type T.
And:When you specify the type parameter, you can access the type parameter from other parts of the method signature as shown.
Finally, the program proves the correctness of the logic in the GetInitializedList method. It prints the values of a five-element List of Booleans, and the values of the three-element List of strings.
Console.WriteLineBool TypeString Type
And:Each of those values has the value we specified in the two method invocations to the GetInitializedList call.
Discussion
Let's examine the C# language specification's description of type parameters in classes and methods. The specification describes in precise detail all of the results for computing type inference matches.
Note:Do not rely on language specification details in your program. Most developers do not study language specifications at length.
