Creating Addins

Start by creating a new class library project and add a reference to the Cake.Core NuGet package via the package manager.

PM> Install-Package Cake.Core

Add the alias method that you want to expose to your Cake script. A script alias method is simply an extension method for ICakeContext that's been marked with the CakeMethodAliasAttribute attribute. The method can make use of any standard CLR features, including optional parameters.

You could also add a script alias property, which works the same way as a script alias method, except that it accepts no arguments and is marked with the CakePropertyAliasAttribute attribute.

using Cake.Core;
using Cake.Core.Annotations;

public static class MyCakeExtension
{
    [CakeMethodAlias]
    public static int GetMagicNumber(this ICakeContext context, bool value)
    {
        return value ? int.MinValue : int.MaxValue;
    }

    [CakeMethodAlias]
    public static int GetMagicNumberOrDefault(this ICakeContext context, bool value, Func<int> defaultValueProvider = null)
    {
        if (value)
        {
            return int.MinValue;
        }

        return defaultValueProvider == null ? int.MaxValue : defaultValueProvider();
    }

    [CakePropertyAlias]
    public static int TheAnswerToLife(this ICakeContext context)
    {
        return 42;
    }
}

Importing Namespaces

Your script alias may need to import one or more namespaces into your Cake script. Cake supports the automatic import of namespaces with attributes.

The CakeNamespaceImportAttribute can be applied at the method, class, or assembly level, or any combination thereof.

// Imports the Cake.Common.IO.Paths namespace into the Cake script for this method only
[CakeNamespaceImport("Cake.Common.IO.Paths")]
public static ConvertableDirectoryPath Directory(this ICakeContext context, string path)
{...}

// Imports the Cake.Common.IO.Paths namespace into the Cake script for any alias method used in the class.
[CakeNamespaceImport("Cake.Common.IO.Paths")]
public static class DirectoryAliases
{...}

// Imports the Cake.Common.IO.Paths namespace into the Cake script for any alias method used in the assembly.
[assembly: CakeNamespaceImport("Cake.Common.IO.Paths")]

Using the addin

Compile the assembly and add a reference to it in the build script via the #r directive.

#r "tools/MyCakeExtension.dll"

Now you should be able to call the method from the script.

Task("GetSomeAnswers")
    .Does(() =>
{
    // Write the values to the console.
    Information("Magic number: {0}", GetMagicNumber(false));
    Information("The answer to life: {0}", TheAnswerToLife);
});