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Tester-Doer Pattern In .Net

This article describes the tester-doer pattern in .NET.

Purpose

The purpose of this pattern is to avoid performance issues that occur due to a potential exception-throwing code.

Potential Exception Throwing Code

Consider the following code: -

List<string> values = someClass.GetAllValues();
Console.WriteLine(values.Count);

The above code is a potential exception-throwing code because the code will throw an exception if the variable values are null. Due to the exception, the code performance degrades. The performance of potential exception-throwing code could be improved using a tester-doer pattern.

Tester-Doer Pattern

In this design pattern, potential exception-throwing code is broken into 2 parts: -

Tester → The code checks the condition.
Doer → The code executes a potentially exception-throwing operation.

Therefore, the preceding code is replaced with: -

List <string> values = someClass.GetAllValues();
if (values != null) // Tester
{
	Console.WriteLine(values.Count); // Doer
}

The code above illustrates the tester-doer pattern.

Posted By -	Karan Gupta

Posted On -	Wednesday, October 14, 2015

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