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Visual Studio 2008
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Design Warnings
 Do not declare static members on ge...
This page is specific to
Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:
Visual Studio Team System
Do not declare static members on generic types

TypeName

DoNotDeclareStaticMembersOnGenericTypes

CheckId

CA1000

Category

Microsoft.Design

Breaking Change

Breaking

An externally visible generic type contains a static (Shared in Visual Basic) member.

When a static member of a generic type is called, the type argument must be specified for the type. When a generic instance member that does not support inference is called, the type argument must be specified for the member. The syntax for specifying the type argument in these two cases is different and easily confused, as the following calls demonstrate:

Visual Basic
' Shared method in a generic type.
GenericType(Of Integer).SharedMethod()

' Generic instance method that does not support inference.
someObject.GenericMethod(Of Integer)()
C#
// Static method in a generic type.
GenericType<int>.StaticMethod();

// Generic instance method that does not support inference.
someObject.GenericMethod<int>();

Generally, both of the prior declarations should be avoided so that the type argument does not have to be specified when the member is called. This results in a syntax for calling members in generics that is no different from the syntax for non-generics. For more information, see Generic methods should provide type parameter.

To fix a violation of this rule, remove the static member or change it to an instance member.

Do not suppress a warning from this rule. Providing generics in a syntax that is easy to understand and use reduces the time that is required to learn and increases the adoption rate of new libraries.

The following example shows a method that causes this violation.

Visual Basic
Imports System
Imports System.Runtime.InteropServices

Namespace Samples

    Public NotInheritable Class EnumParser(Of T)

        Private Sub New()
        End Sub

        ' Fires this violation        
        Public Shared Function TryParse(ByVal value As String, <Out()> ByRef result As T) As Boolean

            Try
                result = DirectCast([Enum].Parse(GetType(T), value), T)
                Return True
            Catch ex As ArgumentException
            End Try

            result = Nothing
            Return False

        End Function

    End Class

    Module Program

        Public Sub Main()

            Dim result As DayOfWeek
            ' Must specify type argument            
            If EnumParser(Of DayOfWeek).TryParse("Monday", result) Then
                Console.WriteLine("Conversion Succeeded!")
            End If

        End Sub

    End Module

End Namespace

C#
using System;

namespace Samples
{    
    public static class EnumParser<T>    
    {        // Fires this violation        
        public static bool TryParse(string value, out T result)        
        {            
            try            
            {                
                result = (T)Enum.Parse(typeof(T), value);                
                return true;            
            }            
            catch (ArgumentException)            
            {            
            }
                result = default(T);            
            return false;        
        }    
    }

    static class Program    
    {        
        public static void Main()        
        {            
            DayOfWeek dayOfWeek;            
            // Must specify type argument            
            if (EnumParser<DayOfWeek>.TryParse("Monday", out dayOfWeek))            
            {                
                Console.WriteLine("Conversion Succeeded!");            
            }        
        }    
    }
}

In the example above, declaring a static member on a generic type forces the user to specify the type argument when calling it.

The following example fixes the above violation by moving the type parameter, T, from the class to the method, allowing it to be inferred by the compiler when called.

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