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bradgonesurfing
bradgonesurfing

Reputation: 32162

Mark a function as "Does not return" in .NET

I have a method in VB.NET which is just a helper for throwing exceptions. It will always throw an exception and never returns However the compiler does not detect this function as a terminating code path and thus I get warning if I use variables later on in the code that are not initialized via the exception code path. 

Function Foo(y as Integer) As Boolean
    dim x as boolean
    if y > 10
        x = 20
    else
        ThrowHelperFunction("Ouch")
    end if
    return x
End Function

The warning is that x is not initialized on all code paths.

Upvotes: 0

Views: 156

Answers (4)

jgauffin
jgauffin

Reputation: 101150

Update:

There is a way since .NET Standard 2.1 (.NET 5 and newer):

[DoesNotReturn]
private void FailFast()
{
    throw new InvalidOperationException();
}

Or conditionally:

private void FailFastIf([DoesNotReturnIf(true)] bool isNull)
{
    if (isNull)
    {
        throw new InvalidOperationException();
    }
}

https://learn.microsoft.com/en-us/dotnet/api/system.diagnostics.codeanalysis.doesnotreturnattribute?view=net-8.0

Original answer:

I don't think that you can change that behavior. Instead you can do something like:

Function Foo(y as Integer) As Boolean
    dim x as boolean
    if y > 10
        x = 20
    else
        throw CreateExceptionHelperFunction("Ouch")
    end if
    return x
End Function

That is, the helper function can still do some processing. But it will return an exception instead of throwing it.

Upvotes: 2

Serge Pavlov
Serge Pavlov

Reputation: 708

There is DoesNotReturnAttribute or this specific reason since .Net Core 2.1.

Upvotes: 1

Jay Jose
Jay Jose

Reputation: 31

try to initialize x with some default value like this. Boolean is Value Type and should never initialize with null value.

Function Foo(y as Integer) As Boolean     
    dim x as boolean     
    x = 0
    if y > 10         
        x = 20     
    else         
        throw CreateExceptionHelperFunction("Ouch")     
    end if     
    return x 
End Function

Upvotes: 1

Nitesh Kumar
Nitesh Kumar

Reputation: 1774

Try to use the following code (use Sub instead of Function)

Sub Foo(y As Integer)
    Dim x As Boolean
    If y > 10 Then
        x = 20
    Else
        ThrowHelperFunction("Ouch")
    End If
End Sub

Thanks.

Upvotes: 0

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