救命，关于datagridview下拉框的。

Question

主要作法：
在datagridview中设置了三个下拉框，是在编辑列中设为DataGridViewComboBoxColumn的办法，然后作成联动的。主要方法就是private void dataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
        {
            //选择类别
            if (e.Control is DataGridViewComboBoxEditingControl && this.dataGridView1.CurrentCell.ColumnIndex == 1 && this.dataGridView1.CurrentCell.RowIndex != -1)
            {
                this.dataGridViewComboBox1 = (DataGridViewComboBoxEditingControl)e.Control;
                //增加委托处理
                dataGridViewComboBox1.SelectionChangeCommitted += new EventHandler(this.dataGridViewComboBox_SelectionChangeCommitted);
            }
            //选择名称
            if (e.Control is DataGridViewComboBoxEditingControl && this.dataGridView1.CurrentCell.ColumnIndex == 3 && this.dataGridView1.CurrentCell.RowIndex != -1)
            {
                this.dataGridViewComboBox2 = (DataGridViewComboBoxEditingControl)e.Control;
                //增加委托处理
                dataGridViewComboBox2.SelectionChangeCommitted += new EventHandler(this.dataGridViewComboBox_SelectionChangeCommittet);
            }
            //选择规格
            if (e.Control is DataGridViewComboBoxEditingControl && this.dataGridView1.CurrentCell.ColumnIndex == 4 && this.dataGridView1.CurrentCell.RowIndex != -1)
            {
                this.dataGridViewComboBox3 = (DataGridViewComboBoxEditingControl)e.Control;
                //增加委托处理
                dataGridViewComboBox3.SelectionChangeCommitted += new EventHandler(this.dataGridViewComboBox_SelectionChangeCommittes);
            }
        }        private void dataGridViewComboBox_SelectionChangeCommitted(object sender, EventArgs e)
        {
            //将相关的值清空
            dataGridView1.Rows[dataGridView1.CurrentCell.RowIndex].Cells[2].Value = "";
            dataGridView1.Rows[dataGridView1.CurrentCell.RowIndex].Cells[4].Value = "";
            dataGridView1.Rows[dataGridView1.CurrentCell.RowIndex].Cells[5].Value = "";
           //处理业务
            DataGridViewComboBoxCell titleCombox = dataGridView1.Rows[dataGridView1.CurrentCell.RowIndex].Cells["item_name"] as DataGridViewComboBoxCell;
            titleCombox.Items.Clear();
            OleDbDataReader readTitle = rkInsert.getread("select item_name from item_table where item_type_name='" + ((ComboBox)sender).Text + "'");
            //Read()方法用来读取SqlDataReader对象中的记录
            while (readTitle.Read())
                titleCombox.Items.Add(readTitle["item_name"].ToString());
            titleCombox.Value = 1; 
            titleCombox.Dispose();
            
        }        private void dataGridViewComboBox_SelectionChangeCommittet(object sender, EventArgs e)
        {
            //处理业务
            DataGridViewComboBoxCell guigiCombox = dataGridView1.Rows[dataGridView1.CurrentCell.RowIndex].Cells["content"] as DataGridViewComboBoxCell;
            guigiCombox.Items.Clear();            OleDbDataReader readGuige = rkInsert.getread("select item_type from item_table where item_name='" + ((ComboBox)sender).Text + "'");
            //Read()方法用来读取SqlDataReader对象中的记录
            while (readGuige.Read())
                guigiCombox.Items.Add(readGuige["item_type"].ToString());
            guigiCombox.Value = 1;
            guigiCombox.Dispose();
            OleDbDataReader readCode = rkInsert.getread("select item_code,item_type,item_unit from item_table where item_name='" + ((ComboBox)sender).Text + "'");
            //Read()方法用来读取SqlDataReader对象中的记录
            readCode.Read();
            if (readCode.HasRows)
            {
                dataGridView1.Rows[dataGridView1.CurrentCell.RowIndex].Cells[2].Value = readCode["item_code"].ToString();
                dataGridView1.Rows[dataGridView1.CurrentCell.RowIndex].Cells[5].Value = readCode["item_unit"].ToString();
            }
            readCode.Close();
        }        private void dataGridViewComboBox_SelectionChangeCommittes(object sender, EventArgs e)
        {
            OleDbDataReader readGuige = rkInsert.getread("select item_code,item_unit from item_table where item_type='" + ((ComboBox)sender).Text + "'");
            //Read()方法用来读取SqlDataReader对象中的记录
            readGuige.Read();
            if (readGuige.HasRows)
            {
                dataGridView1.Rows[dataGridView1.CurrentCell.RowIndex].Cells[2].Value = readGuige["item_code"].ToString();
                dataGridView1.Rows[dataGridView1.CurrentCell.RowIndex].Cells[5].Value = readGuige["item_unit"].ToString();
            }
            readGuige.Close();
        }        private void dataGridView1_CellEndEdit(object sender, DataGridViewCellEventArgs e)
        {
            if (this.dataGridViewComboBox1 != null)
            {
                dataGridViewComboBox1.SelectionChangeCommitted -= new EventHandler(this.dataGridViewComboBox_SelectionChangeCommitted);
                this.dataGridViewComboBox1 = null;
            }
            if (this.dataGridViewComboBox2 != null)
            {
                dataGridViewComboBox2.SelectionChangeCommitted -= new EventHandler(this.dataGridViewComboBox_SelectionChangeCommittet);
                this.dataGridViewComboBox2 = null;
            }
            if (this.dataGridViewComboBox3 != null)
            {
                dataGridViewComboBox3.SelectionChangeCommitted -= new EventHandler(this.dataGridViewComboBox_SelectionChangeCommittes);
                this.dataGridViewComboBox3 = null;
            }
            dataGridView1.Rows[dataGridView1.CurrentCell.RowIndex].Cells[8].Value = Convert.ToDecimal(dataGridView1.Rows[dataGridView1.CurrentCell.RowIndex].Cells[6].Value) * Convert.ToDecimal(dataGridView1.Rows[dataGridView1.CurrentCell.RowIndex].Cells[7].Value);
            sumUpdate();
        }
。
办法是从网上找的，现在问题是，如果一直编辑没有任何问题，但一旦中途把焦点移开datagridview，比如说要修改一下datagridview之外的东西的话，那么重新点击下拉框就会出错，出错方式是这样的，没有提示，只是在点击下拉时下拉框狂闪，而且无法把选中的项目显示在下拉框上，不过实际以经选中了，只是不显示而已，因为我通过联动发现二级的下拉框已经有变化了。不知为什么。

Answer 1

看一下事件有没有问题。如果狂闪可能进入类似死循环状态了。。一点事例：
  #region 显示为下拉框
    private void dgMain_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
    {
      try
      {
        ComboBox cb = (ComboBox)e.Control;
        cb.SelectedIndexChanged += new EventHandler(cb_SelectedIndexChanged);
      }
      catch
      {
        return;
      }
    }
    #endregion    #region 定义下拉框委托
    private void cb_SelectedIndexChanged(object sender,EventArgs e)
    {
      ComboBox combo = (ComboBox)sender;
      if (combo.SelectedValue != null)
      {
        DataRowView drv = (DataRowView)combo.Items[combo.SelectedIndex];
        dgMain.Rows[dgMain.CurrentRow.Index].Cells["CitationTableChineseName"].Value = drv[2].ToString();
      }
    }
    #endregion

Answer 2

http://blog.csdn.net/star19851019/archive/2009/05/20/4203205.aspx是从这儿学的，请大家帮忙看看，倒底怎么回事。