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Anonymous Methods and Code Analysis

An anonymous method is just a method that has no name. Anonymous methods are most frequently used to pass a code block as a delegate parameter.

This topic explains how Code Analysis handles warnings and metrics that are associated with anonymous methods.

Warnings and metrics for an anonymous method that is declared in a member, such as a method or accessor, are associated with the member that declares the method. They are not associated with the member that calls the method.

Description

For example, in the following class, any warnings found in the declaration of anonymousMethod, should be raised against Method1 and not Method2.

Imports System

Delegate Function ADelegate(ByVal value As Integer) As Boolean 

Class AClass

	Sub Method1()
		Dim anonymousMethod As ADelegate = Function(ByVal value As Integer) value > 5
		Method2(anonymousMethod)
	End Sub 

	Sub Method2(ByVal anonymousMethod As ADelegate)
		anonymousMethod(10)
	End Sub 

End Class

Warnings and metrics for an anonymous method declared as an inline assignment to a field are associated with the constructor. If the field is declared as static (Shared in Visual Basic), then the warnings and metrics are associated with the class constructor; otherwise, they are associated with the instance constructor.

Description

For example, in the following class, any warnings found in the declaration of anonymousMethod1, will be raised against the implicitly generated default constructor of Class. Whereas, those found within anonymousMethod2, will be applied against the implicitly generated class constructor.

Imports System

Delegate Function ADelegate(ByVal value As Integer) As Boolean 

Class AClass
	Dim anonymousMethod1 As ADelegate = Function(ByVal value As Integer) value > 5
	Shared anonymousMethod2 As ADelegate = Function(ByVal value As Integer) value > 5
	Sub Method1()
        	anonymousMethod1(10)
        	anonymousMethod2(10)
    	End Sub 
End Class

A class could contain an inline anonymous method that assigns a value to a field that has multiple constructors. In this case, warnings and metrics are associated with all the constructors unless that constructor chains to another constructor in the same class.

Description

For example, in the following class, any warnings found in the declaration of anonymousMethod, should be raised against Class(int) and Class(string), but not against Class().

Imports System

Delegate Function ADelegate(ByVal value As Integer) As Boolean 
Class AClass

	Dim anonymousMethod As ADelegate = Function(ByVal value As Integer) value > 5

	Sub New()
	End Sub 

	Sub New(ByVal a As Integer)
	End Sub 

	Sub New(ByVal a As String)
	End Sub 

End Class

Even though this might seem unexpected, this occurs because the compiler outputs a unique method for every constructor that does not chain to another constructor. Because of this behavior, any violation that occurs within anonymousMethod, must be suppressed separately. This also means that if a new constructor is introduced, warnings that were previously suppressed against Class(int) and Class(string) must also be suppressed against the new constructor.

You can work around this issue in one of two ways. You could declare anonymousMethod in a common constructor that all constructors chain. Or you could declare it in an initialization method that is called by all constructors.

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