Why does ServiceProvider.GlobalProvider.GetService always return null in my command handler?

[aglasencnik]

Hi, I have a quick question.... I have a CommandHandler: ICommandHandler<SaveCommandArgs>
And in the ExecuteCommand I do this:

    public bool ExecuteCommand(SaveCommandArgs args, CommandExecutionContext executionContext)
    {
        try
        {
            var fileName = args.SubjectBuffer.GetFileName();
            if (string.IsNullOrWhiteSpace(fileName))
                return false;

            var fileExtension = Path.GetExtension(fileName);
            if (string.IsNullOrWhiteSpace(fileExtension) || fileExtension.ToLower() != ".dot")
                return false;

            ThreadHelper.ThrowIfNotOnUIThread();
            var package = ServiceProvider.GlobalProvider.GetService(typeof(GraphvizVSPackage)) as GraphvizVSPackage;
            if (package is null)
                return false;

            var window = package.FindToolWindow(typeof(GraphPreviewWindowControl), 0, true);
            if (window is null)
                return false;

            var control = window.Content as GraphPreviewWindowControl;
            if (control is null)
                return false;

            control.UpdatePreviewWindow(fileName);

            return false;
        }
        catch (Exception ex)
        {
            ex.Log();
            return false;
        }
    }

But: var package = ServiceProvider.GlobalProvider.GetService(typeof(GraphvizVSPackage)) as GraphvizVSPackage; is always returned null...
Does anyone maybe know why that is?

[reduckted]

A package is not registered as a service, which is why it can't be retrieved using GetService.

Where are you creating the command handler? Can you pass the package into the command handler's constructor?

[aglasencnik]

Hi, this is the full code:

using Microsoft.VisualStudio.Commanding;
using Microsoft.VisualStudio.Text.Editor;
using Microsoft.VisualStudio.Utilities;
using System.ComponentModel.Composition;
using System.IO;
using GraphvizVS.ToolWindows;
using Microsoft.VisualStudio.Text.Editor.Commanding.Commands;
using Microsoft.VisualStudio.Text;

namespace GraphvizVS.CommandHandlers;

/// <summary>
/// Represents the command handler for save command.
/// </summary>
[Export(typeof(ICommandHandler))]
[Name(nameof(TypeCharCommandHandler))]
[ContentType(ContentTypes.Text)]
[TextViewRole(PredefinedTextViewRoles.PrimaryDocument)]
internal sealed class SaveCommandHandler : ICommandHandler<SaveCommandArgs>
{
    /// <summary>
    /// Gets the display name of the command handler.
    /// </summary>
    public string DisplayName => Vsix.Name;

    /// <summary>
    /// Determines whether command handler is enabled.
    /// </summary>
    /// <param name="args">SaveCommandArgs object.</param>
    /// <returns>CommandState object.</returns>
    public CommandState GetCommandState(SaveCommandArgs args) => CommandState.Available;

    /// <summary>
    /// Executes command handler.
    /// </summary>
    /// <param name="args">TypeCharCommandArgs object.</param>
    /// <param name="executionContext">CommandExecutionContext object.</param>
    /// <returns>Whether key was overriden successfully.</returns>
    public bool ExecuteCommand(SaveCommandArgs args, CommandExecutionContext executionContext)
    {
        try
        {
            var fileName = args.SubjectBuffer.GetFileName();
            if (string.IsNullOrWhiteSpace(fileName))
                return false;

            var fileExtension = Path.GetExtension(fileName);
            if (string.IsNullOrWhiteSpace(fileExtension) || fileExtension.ToLower() != ".dot")
                return false;

            ThreadHelper.ThrowIfNotOnUIThread();
            var package = ServiceProvider.GlobalProvider.GetService(typeof(GraphvizVSPackage)) as GraphvizVSPackage;
            if (package is null)
                return false;

            var window = package.FindToolWindow(typeof(GraphPreviewWindowControl), 0, true);
            if (window is null)
                return false;

            var control = window.Content as GraphPreviewWindowControl;
            if (control is null)
                return false;

            control.UpdatePreviewWindow(fileName);

            return false;
        }
        catch (Exception ex)
        {
            ex.Log();
            return false;
        }
    }
}

[aglasencnik]

Or, do you think I could do it with like normal event handlers?

[reduckted]

Ah, it's a MEF export. 🤦‍♂️ Sorry, I got myself confused between the ICommandHandler and the command interceptors in the toolkit.

Since it's a MEF export, you won't be able to pass the package to the constructor like I suggested, however you should be able to register the package as a service. Doing that will mean you can retrieve it using GetService.

On your package, add this attribute:

[ProvideService(typeof(GraphvizVSPackage), IsAsyncQueryable = true)]
public class GraphvizVSPackage : ToolkitPackage

And then in the InitializeAsync method, add the service:

protected override async Task InitializeAsync(CancellationToken cancellationToken, IProgress<ServiceProgressData> progress)
{
    AddService(typeof(GraphvizVSPackage), (_, _, _) => Task.FromResult<object>(this), promote: true);
    
    // Do other stuff that you need to do when the package is initialized...
}

Now your ServiceProvider.GlobalProvider.GetService(typeof(GraphvizVSPackage)) should work.

Just a note about the promote: true. That promote parameter means:

True if this service should be visible outside this package, otherwise false.

It defaults to false, meaning the service won't be visible outside the package. If a service is not visible outside the package, the only way you can retrieve it is using the package's GetService method. Setting promote to true means you can use the global service provider to retrieve the service.

[aglasencnik]

Does this mean I have to have the autoload on true?

[aglasencnik]

Ok, so it wasn't null, so that's great :) but I got this on the next line:

System.ArgumentException: 'CreateToolWindow only creates Tool Windows derived from ToolWindowPane.'

[aglasencnik]

Ok, if I set the var window = package.FindToolWindow(typeof(GraphPreviewWindowControl), 0, false); to false there is no error, but it is always null...

[aglasencnik]

Ok I found out I have to have GraphPreviewWindow.Pane in the typeof...
Thank you for your help, it means a lot, I couldn't have figured it out on my own :)