Service locator in Windows Workflow Foundation

SampleActivity.cs

public sealed class SampleActivity : CodeActivity
{
    protected override void CacheMetadata(CodeActivityMetadata metadata)
    {
        // Require the IDatabaseContext extension to be defined in the workflow host application.
        // The workflow will fail validation if an extension with this interface is not provided.
        metadata.RequireExtension<IDatabaseContext>();
    }

    protected override void Execute(CodeActivityContext context)
    {
        var db = context.GetExtension<IDatabaseContext>();
    }
}