Interaction between ErrorText and ContextMenuStrip

Question

My application has a datagridview with a RowValidating event handler. If I set ErrorText in RowValidating, it correctly disallows left-clicking on other rows and other controls, but if I have a ContextMenuStrip assigned to another control, the ContextMenuStrip remains active. The user can right-click on the control with the context menu, select a menu item, and the menu events fire.

I've tried all sorts of event handling, but the RowValidating event doesn't fire before the menu is presented, so I can't just disable the context menu in RowValidating. I could perhaps disable the context menu whenever the user is touching any part of the grid, but that has other pitfalls...

I've looked and I don't see any existing writeup on a Microsoft defect or a workaround, or even anyone else encountering the error, so I'm not sure what I could be doing wrong.

Simplified example:

 private void InitializeComponent()
    {
        this.components = new System.ComponentModel.Container();
        this.dataGridView1 = new System.Windows.Forms.DataGridView();
        this.contextMenuStrip1 = new System.Windows.Forms.ContextMenuStrip(this.components);
        this.menuItemToolStripMenuItem = new System.Windows.Forms.ToolStripMenuItem();
        this.textBox1 = new System.Windows.Forms.TextBox();
        this.Column1 = new System.Windows.Forms.DataGridViewTextBoxColumn();
        ((System.ComponentModel.ISupportInitialize)(this.dataGridView1)).BeginInit();
        this.contextMenuStrip1.SuspendLayout();
        this.SuspendLayout();
        this.dataGridView1.Columns.AddRange(new System.Windows.Forms.DataGridViewColumn[] {
        this.Column1});
        this.dataGridView1.RowValidating += new System.Windows.Forms.DataGridViewCellCancelEventHandler(this.dataGridView1_RowValidating);
        this.contextMenuStrip1.Items.AddRange(new System.Windows.Forms.ToolStripItem[] {
        this.menuItemToolStripMenuItem});
        this.menuItemToolStripMenuItem.Text = "Menu Item";
        this.textBox1.ContextMenuStrip = this.contextMenuStrip1;
        this.Controls.Add(this.textBox1);
        this.Controls.Add(this.dataGridView1);

        ((System.ComponentModel.ISupportInitialize)(this.dataGridView1)).EndInit();
        this.contextMenuStrip1.ResumeLayout(false);
        this.ResumeLayout(false);
        this.PerformLayout();

    }

    private System.Windows.Forms.DataGridView dataGridView1;
    private System.Windows.Forms.ContextMenuStrip contextMenuStrip1;
    private System.Windows.Forms.ToolStripMenuItem menuItemToolStripMenuItem;
    private System.Windows.Forms.TextBox textBox1;
    private System.Windows.Forms.DataGridViewTextBoxColumn Column1;


    private void dataGridView1_RowValidating(object sender, DataGridViewCellCancelEventArgs e)
    {
        if (!RowValid(dataGridView1.Rows[e.RowIndex]))
        {
            dataGridView1.Rows[e.RowIndex].ErrorText = "Value must be 5";
            e.Cancel = true;
        }
        else
        {
            dataGridView1.Rows[e.RowIndex].ErrorText = string.Empty;
            e.Cancel = false;
        }
    }

    private bool RowValid(DataGridViewRow row)
    {
        return string.Equals(row.Cells[0].Value, "5");
    }

For reference, these are the events fired in order, note validation does not occur prior to menu opening:

dataGridView1_Enter
dataGridView1_RowEnter
dataGridView1_CellEnter
dataGridView1_CellBeginEdit
contextMenuStrip1_Opening

Answer 1

Handle ToolStripDropDown.Opening event, determine if the context menu should showup or not by setting e.Cancel. Or you can disable the menu item instead.