Hello World (Start TD and create a node)

Let’s create a simple OpenTD program. Start by creating a C# console application in Visual Studio. Look for the template called “Console App (.NET Framework)”, not “.NET Core” or “.NET Standard”. It should look something like this:

Next, add a reference to the OpenTD.dll assembly, which you can find in the GAC. (Try looking under C:\Windows\Microsoft.NET\assembly\GAC_MSIL\OpenTD.) If there are multiple directories, use the one with the highest Assembly Version, which you will see in the directory name, for example “…92.0.0.0_...”.

Add the following code, then compile and run the program:

using OpenTD;
namespace OpenTDGettingStarted
{
    class HelloWorld
    {
        public static void Main(string[] args)
        {
            var td = new ThermalDesktop();
            td.Connect();
            var n = td.CreateNode();
            n.Comment = "Hello World!";
            n.Update();
        }
    }
}

When you run the program, an instance of TD should open and a node should be created at (0, 0, 0). When you edit the node, the comment should be “Hello World!”. If any of these things are not true, check the Troubleshooting section at the end of this guide.

Assuming it worked, let’s examine how. First, we created a ThermalDesktop object called td. This object represents one instance of TD. It has hundreds of methods for interacting with TD models. A single OpenTD client program can create an arbitrary number of ThermalDesktop instances, allowing you to manipulate several models and communicate between them.

Next, we called the ThermalDesktop.Connect() method. By default, this will start a new instance of TD using the latest version of AutoCAD installed. You can control how it works using the ThermalDesktop.ConnectConfig property (Control how OpenTD connects to Thermal Desktop section).

Connect(), like most ThermalDesktop commands, is called synchronously, so it will only return control to your program once it finishes. If there is a problem, it will throw an exception. All OpenTD methods throw exceptions if there is a problem; you do not need to check return values for success.

Once Connect() returned, we called ThermalDesktop.CreateNode() to create a node in TD with default settings. We put the return value in a variable called n. This variable is of type Node and represents the TD node in our client program.

Next, we updated the Comment member of n. This only updated the comment for the client-program Node. To send that update to TD, we called the Node.Update() method. This is an important concept to understand; when you work with objects in your client program that represent objects in TD, they do not automatically propagate their changes to TD. To do that, you need to call the Update() method. (Some objects also haveUpdateFromTD() methods to get the latest changes from TD.)