Casting error in my form

I have a ComboBox in a DataGridView. However I get an error when I run it:

Unable to cast object of type 'System.Windows.Forms.DataGridView' to type 'System.Windows.Forms.ComboBox'.

What can I do to resolve this error?

 ComboBox comboBox;
    private void dataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
    {
        if (e.Control is ComboBox)
        {
            comboBox = e.Control as ComboBox;

            if (dataGridView1.CurrentCell.ColumnIndex >= 0)
            {
                System.Diagnostics.Debug.WriteLine("Edit Control Showing");
                comboBox.SelectedIndexChanged -= new EventHandler(comboBoxItems_SelectedIndexChanged);
                comboBox.SelectedIndexChanged += new EventHandler(comboBoxItems_SelectedIndexChanged);

            }
        }
    }

    void comboBoxItems_SelectedIndexChanged(object sender, EventArgs e)
    {
        try
        {

            int comboBoxSelectedIndex = ((ComboBox)sender).SelectedIndex;
            string comboboxSelectedValue = ((ComboBox)sender).SelectedText;
            int gridViewSelectedRow = dataGridView1.CurrentRow.Index;
            if (comboBoxSelec开发者_如何学JAVAtedIndex >= 0 && gridViewSelectedRow >= 0)
            {
                System.Diagnostics.Debug.WriteLine("ComboBox Index - " + comboBoxSelectedIndex);
                System.Diagnostics.Debug.WriteLine("GridView Index - " + gridViewSelectedRow);
                if (comboBox != null)
                {
                    comboBox.SelectedIndexChanged -= new EventHandler(comboBoxItems_SelectedIndexChanged);



                }
            }
        }
        catch(Exception E)
        {

        }
    }

Looks like this method is also registered to an event of type DataGridView. That is why when you try to cast it (sender) to ComboBox, it throws an exception. Because, in that case, sender is of type DataGridView.

I would also recommend checking the sender object before attempting to cast it (would confirm what decyclone mentioned in his answer in addition to preventing casting errors):

if(sender is ComboxBox) {
      //cast
}

I think somehow you have set the comboBoxItems_SelectedIndexChanged event handler to the DataGridView itself. Check the properties window of DataGridView and if it's there, remove it. Also I recommend using "as" keyword for casting and checking it for "null".