I’m writing a control which inherits from a DataGridView. One of the things I

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Asked: June 3, 20262026-06-03T06:46:44+00:00 2026-06-03T06:46:44+00:00

I’m writing a control which inherits from a DataGridView. One of the things I

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I’m writing a control which inherits from a DataGridView. One of the things I would like to do is to handle the bug whereby a column’s format provider is not used without handling the CellFormatting event (and doing the formatting myself).

I thought I would write an “OnCellFormatting” method which says “if there’s a column format provider, and there’s no CellFormatting event handler(s), do the formatting”.

The important bit (I thought) was “…and there’s no CellFormatting event handler”.

Now, in the past when I’ve written controls with events, I’ve done something like this:

  public event EventHandler SomethingHappened;

  protected void OnSomethingHappened(EventArgs e)
  {
     EventHandler handler = this.SomethingHappened;
     if (handler != null) handler(this, e);
  }

This works fine and my understanding is that this pattern determines if handlers are attached to the event and, if so, invoke those handlers. Fair enough, but why can’t I do this:

  protected void OnCellFormatting(EventArgs e)
  {
     EventHandler handler = this.CellFormatting;
     if (handler == null) DoSomething();
  }

The error is “The event ‘System.Windows.Forms.DataGridView.CellFormatting’ can only appear on the left hand side of += or -=”

What’s different about this (type of) event ?

If I go to the definition of the event, and create my own, ie.

public event DataGridViewCellFormattingEventHandler CellFormatting2

…the compiler is quite happy to assign this to my “handler” variable, so my question is – what’s different with the CellFormatting event (and, one presumes, many others) that I cannot determine if there are any event handlers for it ?

Thanks,
Ross