1、指定DataGridView的第一列為DataGridViewCheckBoxColumn

2、為第一列的標題欄新增一個CheckBox,假設為HeaderCheckBox
同時為HeaderCheckBox定義好 MouseClick 和 KeyUp 事件

private void frmSelectAll_Load(object sender, EventArgs e) 
{
   … 
   
   AddHeaderCheckBox();
   HeaderCheckBox.KeyUp += new KeyEventHandler(HeaderCheckBox_KeyUp);
   HeaderCheckBox.MouseClick += new MouseEventHandler(HeaderCheckBox_MouseClick);
   … 
}

private void AddHeaderCheckBox()
{
    HeaderCheckBox = new CheckBox();
    HeaderCheckBox.Size = new Size(15, 15);

    //Add the CheckBox into the DataGridView
    this.dgvSelectAll.Controls.Add(HeaderCheckBox);
}

private void HeaderCheckBox_MouseClick(object sender, MouseEventArgs e) 
{
    HeaderCheckBoxClick((CheckBox)sender); 
}

private void HeaderCheckBox_KeyUp(object sender, KeyEventArgs e)
{
    if(e.KeyCode == Keys.Space)
       HeaderCheckBoxClick((CheckBox)sender);
}

private void HeaderCheckBoxClick(CheckBox HCheckBox)
{
    IsHeaderCheckBoxClicked = true;

    foreach (DataGridViewRow Row in dgvSelectAll.Rows)
        ((DataGridViewCheckBoxCell)Row.Cells[0]).Value = HCheckBox.Checked;

    dgvSelectAll.RefreshEdit();

    TotalCheckedCheckBoxes = HCheckBox.Checked ? TotalCheckBoxes : 0;

    IsHeaderCheckBoxClicked = false;
}
 

3、以上程式碼發現HeaderCheckBox不在正確的位置顯示
所以新增繪製程式碼，調整位置

private void frmSelectAll_Load(object sender, EventArgs e)
{
   ...
   dgvSelectAll.CellPainting += new DataGridViewCellPaintingEventHandler(dgvSelectAll_CellPainting);   
   ...
}

private void dgvSelectAll_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
{
   if (e.RowIndex == -1 && e.ColumnIndex == 0)
      ResetHeaderCheckBoxLocation(e.ColumnIndex, e.RowIndex);
}

private void ResetHeaderCheckBoxLocation(int ColumnIndex, int RowIndex)
{
    //Get the column header cell bounds
    Rectangle oRectangle = this.dgvSelectAll.GetCellDisplayRectangle(ColumnIndex, RowIndex, true);

    Point oPoint = new Point();

    oPoint.X = oRectangle.Location.X + (oRectangle.Width - HeaderCheckBox.Width) / 2 + 1;
    oPoint.Y = oRectangle.Location.Y + (oRectangle.Height - HeaderCheckBox.Height) / 2 + 1;

    //Change the location of the CheckBox to make it stay on the header
    HeaderCheckBox.Location = oPoint;
}
 

4、到此為止，第一列的顯示，全選/全不選功能已經做好
此時，如果DataGridView的ReadOnly為True，則發現點選CheckBox，無法修改其選中狀態
而設定ReadOnly為false，則發現可以修改CheckBox的狀態，但是DataGridView處於編輯狀態

private void frmSelectAll_Load(object sender, EventArgs e)
{
   ...
   dgvSelectAll.CurrentCellDirtyStateChanged += new EventHandler(dgvSelectAll_CurrentCellDirtyStateChanged);  
   ...
}


private void dgvSelectAll_CurrentCellDirtyStateChanged(object sender, EventArgs e)
{
    if (dgvSelectAll.CurrentCell is DataGridViewCheckBoxCell)
        dgvSelectAll.CommitEdit(DataGridViewDataErrorContexts.Commit);
}
 

注意：如果僅希望第一列可以修改，其他列不能修改，可以把其他列設定為只讀

5、 單擊HeaderCheckBox，讓DataGridView處於全選狀態
然後取消部分記錄的選中狀態，此時HeaderCheckBox仍然為選中狀態，而不是預期中的非選中狀態

private void frmSelectAll_Load(object sender, EventArgs e)
{
   ...
   dgvSelectAll.CellValueChanged += new DataGridViewCellEventHandler(dgvSelectAll_CellValueChanged);
   ...
}

private void dgvSelectAll_CellValueChanged(object sender, DataGridViewCellEventArgs e)
{
    if (!IsHeaderCheckBoxClicked)
        RowCheckBoxClick((DataGridViewCheckBoxCell)dgvSelectAll[e.ColumnIndex, e.RowIndex]);
}   

private void RowCheckBoxClick(DataGridViewCheckBoxCell RCheckBox)
{
    if (RCheckBox != null)
    {
        //Modifiy Counter;            
        if ((bool)RCheckBox.Value && TotalCheckedCheckBoxes < TotalCheckBoxes)
            TotalCheckedCheckBoxes++;
        else if (TotalCheckedCheckBoxes > 0)
            TotalCheckedCheckBoxes--;

        //Change state of the header CheckBox.
        if (TotalCheckedCheckBoxes < TotalCheckBoxes)
            HeaderCheckBox.Checked = false;
        else if (TotalCheckedCheckBoxes == TotalCheckBoxes)
            HeaderCheckBox.Checked = true;
    }
} 

6、IsHeaderCheckBoxClicked的作用
因為HeaderCheckBox狀態的改變，會觸發DataGridView的CellValueChanged事件
而DataGridView的CellValueChanged事件也會導致HeaderCheckBox狀態修改
所以，這裡用了一個全域性變數，來避免程式進入死迴圈