I want to validate the username and password before proceeding with the NSIS install. 

When I click on the next button, I want to check whether the user is authorized to install the application. For this check, I want to make a WCF call from my .NET application. It will return true or false. 

Based on that, I will proceed or abort my installation. I tried using the `CLR::Call /NOUNLOAD` plugin. Since I am referring to a service reference, it is throwing the exception:

`Error calling .net dll method`

Here is the NSIS script that I have so far:

```
Name "Test CLRDLL MakeLogEntry" 
OutFile "TestCLRDLL.exe"
Page instfiles

Section 
    start InitPluginsDir 
    SetOutPath $PLUGINSDIR 
    File "MyDll.dll" 
    CLR::Call /NOUNLOAD "MyDll.dll" "namespace.classname" \ "ValidateLogin" 3 "Myserviceaddress/Servicename.svc"; "username" "password" 
    pop $0 
    MessageBox MB_OK $0 
sectionEnd 

Function .onGUIEnd 
    CLR::Destroy 
FunctionEnd

```