使用来自另一个子的参数调用子

Question

Good day Gurus. Am trying to call a Sub that has parameter from another Sub using Action but not working. Please I have tried to solve this error but couldn't.

I have two Sub in my BasePage in ASP.Net as shown below;

Sub Check(mySub As Action)
    mySub()
End Sub
Sub TestMsg(g As String)
    MsgBox(g)
End Sub

And on click event LinkButton, am trying to call TestMsg through Check as below

Private Sub LinkButton1_Click(sender As Object, e As EventArgs) Handles LinkButton1.Click
    Check(AddressOf TestMsg("Call a sub from another"))
End Sub

But am getting an error message that says addressof operand must be the name of a method (without parenthesis)

Please what is the solution to this?

Thanks in advance

Answer 1

You can get around it with a trick, but it feels like it defeats the purpose

Private Sub LinkButton1_Click(sender As Object, e As EventArgs) Handles LinkButton1.Click
    Check(Sub() TestMsg("Call a sub from another"))
End Sub

To make it work the way you want, you might make a generic overload and call that

Sub Check(mySub As Action)
    mySub()
End Sub
Sub Check(Of T)(mySub As Action(Of T), arg As T)
    mySub(arg)
End Sub
Sub TestMsg(g As String)
    MsgBox(g)
End Sub

Private Sub LinkButton1_Click(sender As Object, e As EventArgs) Handles LinkButton1.Click
    Check(AddressOf TestMsg, "Call a sub from another")
End Sub

Still, it would be easier to just call

TestMsg("Call a sub from another")

Answer 2

vb.net does have "CallByName" feature.

You can specify the sub you call by passing a string name.

So, say this code:

Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

   Dim strSubToCall As String

    strSubToCall = "Sub1"
    CallByName(Me, strSubToCall, CallType.Method)

    strSubToCall = "Sub2"
    CallByName(Me, strSubToCall, CallType.Method, "String value passed")

    strSubToCall = "Sub3"
    CallByName(Me, strSubToCall, CallType.Method, "String value passed", 55)



End Sub

Sub Sub1()

    Debug.Print("Sub 1 called")

End Sub

Sub Sub2(s As String)

    Debug.Print("Sub 2 called - value passed = " & s)

End Sub

Sub Sub3(s As String, i As Integer)

    Debug.Print("Sub 3 called, values passed = " & s & " - " & i.ToString)

End Sub

output:

Sub 1 called
Sub 2 called - value passed = String value passed
Sub 3 called, values passed = String value passed - 55