Generate code or events when drag-drop a custom control from the toolbox

问题

I'm creating a custom control (e.g custom LookUpEdit) and I'm wondering if I can generate code (e.g EditValueChanged event in form.cs file or some rows of code e.g in Form_Load event) automatically while I drag and drop this control inside a form designer, giving this way to any developer the opportunity to easily see and extend this code if he/she wants.

My question is: How to generate code or events automatically in a form (form.cs) when you drag-drop a custom control from the toolbox at design time?

回答1:

Some times you may want to generate some code when dropping a component on form. For example, you can see a similar behavior when you drag a data source from data source window and drop it on form.

The behavior is more common for extensions and add-ins, but you can implement such behavior for your component when dropping from toolbox as well.

The key points in the answer are:

• Creating a new designer for the control by deriving from ControlDesigner
• Creating the event handler using IEventBindingService
• Adding code to the body of the event handler using CodeTypeDeclaration service.

Example

I've created a MyControl control in this example. When you drop an instance of the control on the form, the designer will generate the following code for its Click event:

private void myControl1_Click(object sender, EventArgs e)
{
    MessageBox.Show("Hi!");

}

Here is the code of MyControl and MyControlDesigner. You may want to add null checking to the code.

using System.CodeDom;
using System.Collections;
using System.ComponentModel;
using System.ComponentModel.Design;
using System.Linq;
using System.Windows.Forms;
using System.Windows.Forms.Design;

[Designer(typeof(MyControlDesigner))]
public partial class MyControl : Control
{
}

public class MyControlDesigner : ControlDesigner
{
    public override void InitializeNewComponent(IDictionary defaultValues)
    {
        base.InitializeNewComponent(defaultValues);
        var component = this.Component;
        var eventBindingService = (IEventBindingService)this.GetService(
            typeof(IEventBindingService));
        var componentChangeService = (IComponentChangeService)this.GetService(
            typeof(IComponentChangeService));
        var designerHostService = (IDesignerHost)GetService(typeof(IDesignerHost));
        var uiService = (IUIService)GetService(typeof(IUIService));
        var designerTransaction = (DesignerTransaction)null;
        try
        {
            designerTransaction = designerHostService.CreateTransaction();
            var e = TypeDescriptor.GetEvents(component)["Click"];
            if (e != null)
            {
                var methodName = eventBindingService.CreateUniqueMethodName(component, e);
                var eventProperty = eventBindingService.GetEventProperty(e);
                if (eventProperty.GetValue(component) == null)
                {
                    eventProperty.SetValue(component, methodName);
                    var code = this.GetService(typeof(CodeTypeDeclaration))
                        as CodeTypeDeclaration;
                    CodeMemberMethod method = null;
                    var member = code.Members.Cast<CodeTypeMember>()
                        .Where(x => x.Name == methodName).FirstOrDefault();
                    if (member != null)
                    {
                        method = (CodeMemberMethod)member;
                        method.Statements.Add(
                            new CodeSnippetStatement("MessageBox.Show(\"Hi!\");"));
                    }
                    componentChangeService.OnComponentChanged(component,
                        eventProperty, null, null);
                    eventBindingService.ShowCode(component, e);
                }
            }
            designerTransaction.Commit();
        }
        catch (System.Exception ex)
        {
            if (designerTransaction != null)
                designerTransaction.Cancel();
            uiService.ShowError(ex);
        }
    }
}

来源：https://stackoverflow.com/questions/54212439/generate-code-or-events-when-drag-drop-a-custom-control-from-the-toolbox