Answer.

In Visual Basic .NET, anonymous methods are implemented using lambda expressions (Function or Sub). They allow defining small code blocks without creating a separate named procedure. Example usage:

Dim squared = Function(x As Integer) x * x
Console.WriteLine(squared(5)) ' Output: 25

Dim numbers = {1, 2, 3, 4}
Dim evens = numbers.Where(Function(n) n Mod 2 = 0)
For Each n In evens
    Console.WriteLine(n)
Next

Advantages:

• Simplifies code by eliminating unnecessary names and declarations.
• Well-suited for short event handlers or LINQ expressions.
• Allows "closing over" external variables (closure).

Limitations:

• Does not support all VB constructs, such as attributes.
• Generally less convenient for complex logic — named procedures are better for that.

Trick Question.

Question: "Can a lambda expression be used to declare a procedure with a GoTo statement inside? Why?"

Correct answer: No, lambda expressions in VB.NET do not allow the use of flow control tools like GoTo, GoSub, or Label. This is due to the specifics of the implementation of anonymous methods. Attempting to use GoTo will result in a compilation error.

Example code (will produce an error):

Dim broken = Sub()
    GoTo Label1
    Label1:
End Sub

Examples of real errors caused by a lack of knowledge on the topic.

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Story

In a data processing project, we tried to use lambda expressions for complex validation with multiple exit points via GoTo. When migrating from regular methods to lambda code, we encountered a compilation error and had to urgently change the function architecture.

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Story

For asynchronous calls, we used anonymous methods. Inside the lambda, we accidentally referenced variables that changed in a loop. This led to unexpected results, as the lambda "remembered" the variable by reference rather than by value — resulting in mysterious bugs in the reports.

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Story

In one project, we directly converted anonymous methods to incompatible delegate types (for example, Sub instead of Function). The compiler did not produce an explicit error, but the event handlers did not execute. This was discovered only during manual testing, causing a release delay.