Do not ignore method results

Cause

A constructor or method is called that creates and returns a new object, and the new object is neither used nor assigned to a variable.

Rule Description

Unnecessary object creation and the associated garbage collection of the unused object degrade performance.

How to Fix Violations

To fix a violation of this rule, use the new object or remove the method or constructor call.

When to Exclude Warnings

Do not exclude a warning from this rule unless the act of creating the object serves some purpose.

Example

The following example shows a class that ignores the result of calling String.Trim.

Imports System
Imports System.Globalization

Namespace PerformanceLibrary

   Public Class IgnoredMethodResults
   
      Sub Violations()
      
         Dim violationOne As String = "lo"
         Dim violationTwo As String = "MediuM "

         violationOne.ToUpper(CultureInfo.InvariantCulture)
         violationTwo.ToLower(CultureInfo.InvariantCulture).Trim()

      End Sub

   End Class

End Namespace

using System;
using System.Globalization;

namespace PerformanceLibrary
{
   public class IgnoredMethodResults
   {
      public void Violations()
      {
         "violationOne".ToUpper(CultureInfo.InvariantCulture);

         string violationTwo = "MediuM ";
         violationTwo.ToLower(CultureInfo.InvariantCulture).Trim();

         new Random();
      }
   }
}

The following example fixes the above violation by assigning the result of String.Trim back to the variable it was called on.

The following example shows a method that does not use an object that it creates.

Note
This violation cannot be reproduced in Visual Basic.

The following example fixes the above violation by removing the unnecessary creation of an object.