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CA1007: Use generics where appropriate


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The latest version of this topic can be found at CA1007: Use generics where appropriate.

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An externally visible method contains a reference parameter of type System.Object, and the containing assembly targets .NET Framework 2.0.

A reference parameter is a parameter that is modified by using the ref (ByRef in Visual Basic) keyword. The argument type that is supplied for a reference parameter must exactly match the reference parameter type. To use a type that is derived from the reference parameter type, the type must first be cast and assigned to a variable of the reference parameter type. Use of a generic method allows all types, subject to constraints, to be passed to the method without first casting the type to the reference parameter type.

To fix a violation of this rule, make the method generic and replace the Object parameter by using a type parameter.

Do not suppress a warning from this rule.

The following example shows a general-purpose swap routine that is implemented as both nongeneric and generic methods. Note how efficiently the strings are swapped by using the generic method compared to the nongeneric method.

using System;

namespace DesignLibrary
   public sealed class ReferenceParameters
      private ReferenceParameters(){}

      // This method violates the rule.
      public static void Swap(ref object object1, ref object object2)
         object temp = object1;
         object1 = object2;
         object2 = temp;

      // This method satifies the rule.
      public static void GenericSwap<T>(ref T reference1, ref T reference2)
         T temp = reference1;
         reference1 = reference2;
         reference2 = temp;

   class Test
      static void Main()
         string string1 = "Swap";
         string string2 = "It";

         object object1 = (object)string1;
         object object2 = (object)string2;
         ReferenceParameters.Swap(ref object1, ref object2);
         string1 = (string)object1;
         string2 = (string)object2;
         Console.WriteLine("{0} {1}", string1, string2);

         ReferenceParameters.GenericSwap(ref string1, ref string2);
         Console.WriteLine("{0} {1}", string1, string2);

CA1005: Avoid excessive parameters on generic types

CA1010: Collections should implement generic interface

CA1000: Do not declare static members on generic types

CA1002: Do not expose generic lists

CA1006: Do not nest generic types in member signatures

CA1004: Generic methods should provide type parameter

CA1003: Use generic event handler instances