如何创建进行异步调用的自定义 PropertyGrid 编辑器？

Question

I have a custom PropertyGrid editor that launches a form and allows the user to make some selections. These selections are used to provide the property value. The form makes a call to a web service to retrieve data for the user to choose from. Currently, this web service call is done synchronously. From what I understand, such calls should ideally be made asynchronously, so as not to freeze the application.

Is there a way that I could do this asynchronously?

It seems like I would need to make my EditValue method async, but the class that I am over-riding (UITypeEditor) does not appear to have this option.

This answer provides a nice background for how I have my custom PropertyGrid editor implemented. However, I will also provide a very basic code snippet to provide a rough idea of what I am trying to do. I'm not using a form in this example, but the important thing to understand is that I am trying to await an async call within my EditValue method.

class FooEditor : UITypeEditor
{
    public override UITypeEditorEditStyle GetEditStyle(ITypeDescriptorContext context)
    {
        return UITypeEditorEditStyle.Modal;
    }
    public override object EditValue(ITypeDescriptorContext context, System.IServiceProvider provider, object value)
    {
        using (var client = MasterContainer.Resolve<ValueWebClient>())
        {
            var value = await client.GetCurrentValue(); // visual studio shows await can only be used in async method error
            return value;
        }
    }
}

I suppose one approach might be to load all of your data up-front so that you don't have to make the call. However, the data could be changed while the user is working, so I would prefer not to take that approach.

Answer 1

You can't use the async keyword in the EditValue method without changing the return type of the method to Task<object> .

Assuming you own the UITypeEditor base class, this would be a good option.

The current API ( object EditValue(ITypeDescriptorContext context, System.IServiceProvider provider, object value ) is indeed synchronous though and it's not much you can do about it I am afraid. Loading all data up-front seems to be a good compromise.