MethodInfo.Invoke Return Values

[DerPflug]

I am having a problem returning a value from an invoked method. The class I'm instantiating is as follows:

Public Class DoItClass

    Public Function GetAValue(ByVal p_intType As Integer, ByRef p_strWhichType As String) As String

        Select Case p_intType
            Case 1
                p_strWhichType = "One"
            Case 2
                p_strWhichType = "Two"
        End Select

        Return "GetAValue was accessed"

    End Function
End Class

The app that calls this function looks like the following:

dim strMethodName As String = "GetAValue"
dim strClassName As string = "DoItClass"
Dim objAssembly As Assembly
Dim objClass As Object
Dim objType As Type
Dim objMethod As MethodInfo
Dim objParamArray() As Object = {1,""}
Dim strReturnMessage As String

try
objAssembly = Assembly.LoadFrom("C:\MyDynamicClass.dll")

For Each objType In objAssembly.GetTypes
    If objType.FullName.EndsWith("." + strClassName) Then
          objClass = objAssembly.CreateInstance(objType.FullName.ToString)
          objMethod = objType.GetMethod(strMethod)
          strReturnMessage = CType(objMethod.Invoke(objClass, objParamArray), String)
          strByRefParm = objParamArray(1).ToString
          exit for
    End If
Next
Catch ex as Exception
     Messagebox.show(ex.message)
End Try

The error I get is "System.Reflection.TargetParameterCountException". When I change my method to a sub and just call the Invoke function without attempting to return anything it executes fine. I feel there's something obvious eluding me here. Thanks for any suggestions.

 

[chrissie1]

Find the subtle differences.

[Blue]Imports[/Blue] System.Reflection

[Blue]Public[/Blue] [Blue]Class[/Blue] Form2

    [Blue]Private[/Blue] [Blue]Sub[/Blue] Button1_Click([Blue]ByVal[/Blue] sender [Blue]As[/Blue] System.Object, [Blue]ByVal[/Blue] e [Blue]As[/Blue] System.EventArgs) [Blue]Handles[/Blue] Button1.Click
        [Blue]Dim[/Blue] strMethodName [Blue]As[/Blue] [Blue]String[/Blue] = [Red]"GetAValue"[/Red]
        [Blue]Dim[/Blue] strClassName [Blue]As[/Blue] [Blue]String[/Blue] = [Red]"DoItClass"[/Red]
        [Blue]Dim[/Blue] objAssembly [Blue]As[/Blue] Assembly
        [Blue]Dim[/Blue] objClass [Blue]As[/Blue] Object
        [Blue]Dim[/Blue] objType [Blue]As[/Blue] Type
        [Blue]Dim[/Blue] objMethod [Blue]As[/Blue] MethodInfo
        [Blue]Dim[/Blue] objParamArray() [Blue]As[/Blue] Object = {1, [Red]""[/Red]}
        [Blue]Dim[/Blue] objReturnMessage [Blue]As[/Blue] Object
        [Blue]Dim[/Blue] strbyrefparm [Blue]As[/Blue] [Blue]String[/Blue]

        [Blue]Try[/Blue]
            objAssembly = Assembly.GetExecutingAssembly

            [Blue]For[/Blue] Each objType In objAssembly.GetTypes
                [Blue]If[/Blue] objType.FullName.EndsWith([Red]"."[/Red] + strClassName) [Blue]Then[/Blue]
                    objClass = objAssembly.CreateInstance(objType.FullName.ToString)
                    objMethod = objType.GetMethod(strMethodName)
                    objReturnMessage = objMethod.Invoke(objClass, objParamArray)
                    strByRefParm = objParamArray(1).ToString
                    [Blue]Exit[/Blue] [Blue]For[/Blue]
                [Blue]End[/Blue] [Blue]If[/Blue]
            [Blue]Next[/Blue]
        [Blue]Catch[/Blue] ex [Blue]As[/Blue] Exception
            MessageBox.Show(ex.Message)
        [Blue]End[/Blue] [Blue]Try[/Blue]

    [Blue]End[/Blue] [Blue]Sub[/Blue]
[Blue]End[/Blue] [Blue]Class[/Blue]

[Blue]Public[/Blue] [Blue]Class[/Blue] DoItClass

    [Blue]Public[/Blue] [Blue]Function[/Blue] GetAValue([Blue]ByVal[/Blue] p_intType [Blue]As[/Blue] [Blue]Integer[/Blue], [Blue]ByRef[/Blue] p_strWhichType [Blue]As[/Blue] [Blue]String[/Blue]) [Blue]As[/Blue] [Blue]String[/Blue]

        Select Case p_intType
            Case 1
                p_strWhichType = [Red]"One"[/Red]
            Case 2
                p_strWhichType = [Red]"Two"[/Red]
        [Blue]End[/Blue] Select

        [Blue]Return[/Blue] [Red]"GetAValue was accessed"[/Red]

    [Blue]End[/Blue] [Blue]Function[/Blue]
[Blue]End[/Blue] [Blue]Class[/Blue]

Christiaan Baes
Belgium

"My old site" - Me