Create a CSharp DLL for Xojo

This example shows how to create a simple function that adds two numbers together by creating a simple DLL in C# with Visual Studio 2019 that can be used in Xojo 2020 r1. The two major aspects are to: 1) Install the Microsoft Build Tools 2015, and 2) RGiesecke NuGet package.

*Uses Xojo API2

CSharpXojoScreenGrab

Here are the steps to create the plugin in Visual Studio 2019 and read the DLL in Xojo:

Download Microsoft Build Tools 2015 and install from: https://www.microsoft.com/en-us/download/confirmation.aspx?id=48159
Start Visual Studio 2019
Create a New Project
Select C# Class Library (.NET Framework) and press Next
Create a folder where to store project (I am using C:\test\CSharpXojo\)
Project name is CSXojo and press Create
Tools->NuGet package manager->Manage NuGet Packages for Solution
Browse and choose->Unmanaged Exports by Robert Giesecke->Click on CSXojo in right panel->Select Install
Select Release, CPU Manager and choose Configuration: Release, Platform: x64, Build (checked)
The following code in Class1.cs should look like the following:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using RGiesecke.DllExport;

namespace CSXojo

{

public class Class1

{

[DllExport]

public static int AddTwo(int x, int y)

{

return x + y;

}

Select Build->Build solution
Create a new Xojo desktop project
Save the project in C:\test and name the project XojoCSharp.xojo_binary_project
Select Windows x86 64-bit build
Add a label and a button, add action event to button and the following code:

Declare Function AddTwo Lib "C:\test\CSharpXojo\CSXojo\CSXojo\bin\x64\Release\CSXojo.dll" (x as Integer, y as Integer) As Integer

LblAnswer.Text = CStr(AddTwo(145,1023))

Run the 64-bit Xojo program and pressing the OK button will show an answer of 1168. Well done!!!!!

The code is available on Github at: CSharpDLLXojo Github Link