VB.NET Function - Return vs Assignment

What is the difference between this two ways of returning value in a function in VB.NET?

Using Return Statement:

Public Function Foo() As String
    Return "Hello World"
End Function

Using Assignment:

Public Function Foo() As String
    Foo = "Hello World"
End Function

I'm using the first one then I saw someone using the second. I wonder if there's a benefit I could get using the second.

Its a legacy carry over from basic days.

Return will leave the scope immediately, while assignment wont.

Think of it this way:

Public Function Foo() As String
    Foo = "Hello World"
    OtherFunctionWithSideEffect()
End Function

vs

Public Function Foo() As String
    Return "Hello World"
    OtherFunctionWithSideEffect()
End Function

Now can you see the difference?

In practice, modern VB.Net should almost always prefer the latter style (Return).

Testing this in LinqPad:

Public Function myString() As String    
    Return "Hello World"
End Function

Public Function myString2() As String
    myString2 = "Hello World"
End Function

Here's the IL output:

myString:
IL_0000:  ldstr       "Hello World"
IL_0005:  ret         

myString2:
IL_0000:  ldstr       "Hello World"
IL_0005:  stloc.0     
IL_0006:  ldloc.0     
IL_0007:  ret 

So in a sense the IL would add two more lines but this is a small diffence i think.

Both are valid but using Return saves having to add Exit Function if you want to return part way through a function so it is preferable:

If param.length=0 then
    Msgbox "Invalid parameter length"
    Return Nothing
End If

Compare with:

If param.length=0 then
    Msgbox "Invalid parameter length"
    Foo = Nothing
    Exit Function
End If

Also If you use Return you don't have to remember to right click Rename to rename all instances of Foo to FooNew if you decide to change the name of your function.

Alongside the other answers, there is also a difference, as follows:

Public Function Test() As Integer
  Try
    Dim retVal as Integer = 0
    retVal = DoSomethingExceptional()
  Catch ex as Exception ' bad practice, I know
  Finally
  Test = retVal
  End Try
End Function

You can't put a Return in a Finally block, but you can assign the value of the function there.