C# RichTextBox与Microsoft公式编辑器更新异常问题求助

Hey there, let's tackle this frustrating issue where your RichTextBox doesn't show updated formula content after you edit it in the Microsoft Equation Editor. I've run into similar OLE object display quirks with WinForms before, so here's what's going on and how to fix it:

What's Causing the Problem? #

When you edit an embedded Equation Editor object, the underlying RTF content does get updated (which is why you see the changes when you double-click again), but the WinForms RichTextBox doesn't automatically refresh its display to reflect those changes. This is because the control relies on cached rendering for performance, and it doesn't listen for the specific OLE object update notification by default.

Step-by-Step Solutions #

1. Custom RichTextBox with OLE Update Handling (Recommended) #

Create a custom RichTextBox that listens for the EN_OLEUPDATE notification (sent when an embedded OLE object is modified) and forces a display refresh. Here's the code:

using System.Windows.Forms;

namespace Panel.Views
{
    public class CustomRichTextBox : RichTextBox
    {
        private const int WM_COMMAND = 0x0111;
        private const int EN_OLEUPDATE = 0x0400 + 108; // Notification code for OLE object updates

        protected override void WndProc(ref Message m)
        {
            if (m.Msg == WM_COMMAND)
            {
                int notifyCode = m.WParam.ToInt32() >> 16;
                if (notifyCode == EN_OLEUPDATE)
                {
                    // Force the control to refresh its display
                    Invalidate();
                    Update();
                }
            }
            base.WndProc(ref m);
        }
    }
}

How to Use This:

• Open your form's designer, delete the existing richTextBox1.
• Drag your new CustomRichTextBox from the toolbox (you may need to build the project first for it to appear) onto the form, and name it richTextBox1 to match your existing code.
• Run the app again—after editing and exiting the Equation Editor, the RichTextBox should now show your updated formula immediately.

2. Quick Test with Manual Refresh #

If you want to verify the issue is just a display refresh problem before implementing the custom control, add a button to manually refresh the RichTextBox:

private void btnRefresh_Click(object sender, EventArgs e)
{
    richTextBox1.Refresh();
}

After editing your formula and exiting the editor, click this button—you should see the updated content. This confirms the display cache is the culprit.

3. Alternative: SelectionChanged Event Refresh #

You can also hook into the RichTextBox's SelectionChanged event to trigger a refresh whenever the user interacts with the control:

private void richTextBox1_SelectionChanged(object sender, EventArgs e)
{
    richTextBox1.Refresh();
}

This is simpler but may cause unnecessary refreshes during normal text editing, so the custom control approach is cleaner for OLE-specific updates.

Additional Checks #

• Make sure your Panel.Properties.Resources.Plot1_x_axis is valid RTF containing the Equation Editor OLE object.
• Confirm the RichTextBox isn't set to ReadOnly (this can block display updates for OLE objects).
• Ensure the control's Enabled property is set to true.

内容的提问来源于stack exchange，提问作者Marcin