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CA1804: Remove unused locals


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The latest version of this topic can be found at CA1804: Remove unused locals.

|Breaking Change|Non-breaking|

A method declares a local variable but does not use the variable except possibly as the recipient of an assignment statement. For analysis by this rule, the tested assembly must be built with debugging information and the associated program database (.pdb) file must be available.

Unused local variables and unnecessary assignments increase the size of an assembly and decrease performance.

To fix a violation of this rule, remove or use the local variable. Note that the C# compiler that is included with .NET Framework 2.0 removes unused local variables when the optimize option is enabled.

Suppress a warning from this rule if the variable was compiler emitted. It is also safe to suppress a warning from this rule, or to disable the rule, if performance and code maintenance are not primary concerns.

The following example shows several unused local variables.

using System;
using System.Windows.Forms;

namespace PerformanceLibrary
   public class UnusedLocals
      public void SomeMethod()
         int unusedInteger;
         string unusedString = "hello";
         string[] unusedArray = Environment.GetLogicalDrives();
         Button unusedButton = new Button();

CA1809: Avoid excessive locals

CA1811: Avoid uncalled private code

CA1812: Avoid uninstantiated internal classes

CA1801: Review unused parameters