Technical Document

Summary

The following document outlines how to interface with QAS API’s using the C#.NET development environment.

Solution

1. Interfacing with the DLL

The way to interface with the dll in C# is to use the DllImport command as indicated below followed by the name of the dll. This example shows how to integrate with the QAS Rapid API.

[DllImport("qaruieb.dll", CharSet=CharSet.Ansi)] public static extern

int QARapid_ListItem(int vl1

,[MarshalAs(UnmanagedType.LPStr)]StringBuilder sBuffer,int vi3 , int vi4

);

Also notice that buffers such as sBuffer which need to retain information should be declared using MarshalAs and the StringBuilder Object as described in the next section.

2. Using the C# StringBuilder Object

In C# the correct way to pass a string by reference is to use a StringBuilder Object (System.text.stringbuilder). For example, the following sample code illustrates how to display the first item resulting from a search on BA99lt:

int icode;

StringBuilder rsBuffer = new StringBuilder(100);

icode=QARapid_Open("","");

icode=QARapid_Search("BA99lt");

icode=QARapid_ListItem(0,rsBuffer,0,100);

MessageBox.Show(rsBuffer.ToString(0,rsBuffer.Length));

Common Problems

The most common is failure to retain address information after making a function call. This is due to the fact that some elements need to be passed by reference.

Symptoms of an address not being returned correctly:

The symptoms are normally very easy to detect and commonly will result in blank spaces or garbage being returned to the address buffer. When this happens it is a good idea to set up API logging (see the link below) to confirm that nothing is being passed back and retained.

Related links

How do I solve problems with QAS API integrations?