private void dgvVar_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
        {
            if (this.dgvVar.CurrentCell != null && this.dgvVar.CurrentCell.OwningColumn.Name == "colVarType")
            {
                ComboBox cb = e.Control as ComboBox;
                cb.SelectedIndexChanged += new EventHandler(FormIntelligenceDocument_SelectedIndexChanged);
            }
        }

        void FormIntelligenceDocument_SelectedIndexChanged(object sender, EventArgs e)
        {
            ComboBox cb = sender as ComboBox;
            if (cb != null)   
         {
                if (cb.Text == "其它字典")
                    this.dgvVar.CurrentRow.Cells["colVarZD"].Value = this._VarTypeZD.Rows[0]["Code"];
                else
                    this.dgvVar.CurrentRow.Cells["colVarZD"].Value = null;
                ////让变量类型失去焦点
                //this.dgvVar.EndEdit();

                //(sender as ComboBox).SelectedIndexChanged -= new EventHandler(FormIntelligenceDocument_SelectedIndexChanged);
            }
        }

       private void dgvVar_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
        {
cb.SelectedIndexChanged -= new EventHandler(FormIntelligenceDocument_SelectedIndexChanged);

            if (this.dgvVar.CurrentCell != null && this.dgvVar.CurrentCell.OwningColumn.Name == "colVarType")
            {
                ComboBox cb = e.Control as ComboBox;
                cb.SelectedIndexChanged += new EventHandler(FormIntelligenceDocument_SelectedIndexChanged);
            }
        }

------解决方案--------------------
探讨


就设置了这两个属性    
        dgvCbx.DisplayStyle = DataGridViewComboBoxDisplayStyle.Nothing;
        dgvCbx.FlatStyle = FlatStyle.Popup;