Function does not return value in all code paths error

[VB.NET Developer]

Hi,
I am facing "issue" "Function does not return value in all code paths" when clicking on a button. It is not really an issue since it works fine within app itself. The problem is when executing app via play button - I have got a lot of a first chance exception occured in.... I have tried resolve it via Return statement - https://www.vbforums.com/showthread....=1#post3293950, but my function does not contains IF condition.

[PlausiblyDamp]

Hi,
I am facing "issue" "Function does not return value in all code paths" when clicking on a button. It is not really an issue since it works fine within app itself. The problem is when executing app via play button - I have got a lot of a first chance exception occured in.... I have tried resolve it via Return statement - https://www.vbforums.com/showthread....=1#post3293950, but my function does not contains IF condition.

Could you post the function in question?

It doesn't always have to be an If statement that causes this, any time there is more than one possible way to exit a function (other than throwing an exception) all of the possible ways need to return something. If you have an If, a select case, or just don't have a return statement at the end you can get this error.

[dday9]

Here are two examples of when the exception would occur:

Private Function Foo(input As String) As String
    If (input = "foo") Then
        Return "hello world"
    End If
End Function

Private Function Bar() As String
    Select Case DateTime.Now.Minute
        Case 0
            Return "Hello World
    End Select
End Function

In the first instance, if the input parameter is not "foo" then the function will not return a value. In the second instance, if the current minute is not 0 then the function will not return a value.

If you require a value or require that a value have a particular value, then you should throw an exception (or return a default value) when the condition isn't met. For example, let's use a real life scenario where I have a dictionary that holds an item off a restaurant menu as its key and the respective price as its value. If I were creating a function to get the price and then apply sales tax to it, then I would throw an exception if the value passed to the function is not in the menu:

Private Function GetTotalCost(item As String) As Double
    If (String.IsNullOrWhiteSpace(item)) Then
        Throw New ArgumentNullException("item")
    End If
    If (Not _menu.ContainsKey(item)) Then
        Throw New ArgumentException(item & " is not a valid menu item.")
    End If

    Dim itemCost As Double = _menu(item)
    Dim applicableTax As Double = itemCost * _salesTax

    Return itemCost * applicableTax
End Function

Fiddle: https://dotnetfiddle.net/sr0ASS

The incorrect way to write this function that would generate the error in question would be:

Private Function GetTotalCost(item As String) As Double
    If (Not String.IsNullOrWhiteSpace(item) AndAlso _menu.ContainsKey(item)) Then
        Dim itemCost As Double = _menu(item)
        Dim applicableTax As Double = itemCost * _salesTax
        Return itemCost * applicableTax
    End If
End Function

[Niya]

The problem is when executing app via play button - I have got a lot of a first chance exception occured in....

I find this interesting. That shouldn't be throwing an exception. That warning is just that, a warning.