DataGridView的CellFormatting事件和CellPainting事件-阿里云开发者社区

1、CellFormatting事件，一般重绘单元格属性。
    private Bitmap highPriImage;
    private Bitmap mediumPriImage;
    private Bitmap lowPriImage;
private void dataGridView1_CellFormatting(object sender,
        System.Windows.Forms.DataGridViewCellFormattingEventArgs e)
    {
        // Set the background to red for negative values in the Balance column.
        if (dataGridView1.Columns[e.ColumnIndex].Name.Equals("Balance"))
        {
            Int32 intValue;
            if (Int32.TryParse((String)e.Value, out intValue) &&
                (intValue < 0))
            {
                e.CellStyle.BackColor = Color.Red;
                e.CellStyle.SelectionBackColor = Color.DarkRed;
            }
        }

        // Replace string values in the Priority column with images.
        if (dataGridView1.Columns[e.ColumnIndex].Name.Equals("Priority"))
        {
            // Ensure that the value is a string.
            String stringValue = e.Value as string;
            if (stringValue == null) return;

            // Set the cell ToolTip to the text value.
            DataGridViewCell cell = dataGridView1[e.ColumnIndex, e.RowIndex];
            cell.ToolTipText = stringValue;

            // Replace the string value with the image value.
            switch (stringValue)
            {
                case "high":
                    e.Value = highPriImage;
                    break;
                case "medium":
                    e.Value = mediumPriImage;
                    break;
                case "low":
                    e.Value = lowPriImage;
                    break;
            }
        }
    }

2 、CellPainting事件，一般用于合并单元格用
Windows Forms DataGridView 没有提供合并单元格的功能，要实现合并单元格的功能就要在CellPainting事件中使用Graphics.DrawLine和 Graphics.DrawString 自己来“画”。
下面的代码可以对DataGridView第1列内容相同的单元格进行合并：
#region" 合并单元格的测试 "
private int? nextrow = null;
private int? nextcol = null;
private void dataGridView1_CellFormatting(object sender, System.Windows.Forms.DataGridViewCellFormattingEventArgs e)
{
    if (this.dataGridView1.Columns["description"].Index == e.ColumnIndex && e.RowIndex >= 0)
    {
        if (this.nextcol != null & e.ColumnIndex == this.nextcol)
        {
            e.CellStyle.BackColor = Color.LightBlue;
            this.nextcol = null;
        }
        if (this.nextrow != null & e.RowIndex == nextrow)
        {
            e.CellStyle.BackColor = Color.LightPink;
            this.nextrow = null;
        }
        if (e.RowIndex != this.dataGridView1.RowCount - 1)
        {
            if (e.Value.ToString() == this.dataGridView1.Rows[e.RowIndex + 1].Cells[e.ColumnIndex].Value.ToString())
            {
                e.CellStyle.BackColor = Color.LightPink;
                nextrow = e.RowIndex + 1;
            }
        }

    }
    if (this.dataGridView1.Columns["name"].Index == e.ColumnIndex && e.RowIndex >= 0)
    {
        if (e.Value.ToString() == this.dataGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex + 1].Value.ToString())
        {
            e.CellStyle.BackColor = Color.LightBlue;
            nextcol = e.ColumnIndex + 1;
        }
    }
}
//==========================

//绘制单元格
private void dataGridView1_CellPainting(object sender, System.Windows.Forms.DataGridViewCellPaintingEventArgs e)
{

    //纵向合并
    if (this.dataGridView1.Columns["description"].Index == e.ColumnIndex && e.RowIndex >= 0)
    {

        using (
            Brush gridBrush = new SolidBrush(this.dataGridView1.GridColor),
            backColorBrush = new SolidBrush(e.CellStyle.BackColor))
        {
            using (Pen gridLinePen = new Pen(gridBrush))
            {
                // 擦除原单元格背景
                e.Graphics.FillRectangle(backColorBrush, e.CellBounds);
                //// 绘制线条,这些线条是单元格相互间隔的区分线条 ,
                ////因为我们只对列name做处理,所以datagridview自己会处理左侧和上边缘的线条
                if (e.RowIndex != this.dataGridView1.RowCount - 1)
                {
                    if (e.Value.ToString() != this.dataGridView1.Rows[e.RowIndex + 1].Cells[e.ColumnIndex].Value.ToString())
                    {

                        e.Graphics.DrawLine(gridLinePen, e.CellBounds.Left, e.CellBounds.Bottom - 1,
                        e.CellBounds.Right - 1, e.CellBounds.Bottom - 1);//下边缘的线
                        // 绘制值
                        if (e.Value != null)
                        {
                            e.Graphics.DrawString((String)e.Value, e.CellStyle.Font,
                                Brushes.Crimson, e.CellBounds.X + 2,
                                e.CellBounds.Y + 2, StringFormat.GenericDefault);
                        }
                    }
                }
                else
                {
                    e.Graphics.DrawLine(gridLinePen, e.CellBounds.Left, e.CellBounds.Bottom - 1,
                        e.CellBounds.Right - 1, e.CellBounds.Bottom - 1);// 下边缘的线
                    // 绘制值
                    if (e.Value != null)
                    {
                        e.Graphics.DrawString((String)e.Value, e.CellStyle.Font,
                            Brushes.Crimson, e.CellBounds.X + 2,
                            e.CellBounds.Y + 2, StringFormat.GenericDefault);
                    }
                }
                // 右侧的线
                e.Graphics.DrawLine(gridLinePen, e.CellBounds.Right - 1,
                    e.CellBounds.Top, e.CellBounds.Right - 1,
                    e.CellBounds.Bottom - 1);

                e.Handled = true;
            }
        }
    }

    //横向合并
    if (this.dataGridView1.Columns["name"].Index == e.ColumnIndex && e.RowIndex >= 0)
    {

if (e.Value.ToString() != this.dataGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex + 1].Value.ToString())
{

                    //右侧的线
                    e.Graphics.DrawLine(gridLinePen, e.CellBounds.Right - 1, e.CellBounds.Top,
                        e.CellBounds.Right - 1, e.CellBounds.Bottom - 1);
                    // 绘制值
                    if (e.Value != null)
                    {
                        e.Graphics.DrawString((String)e.Value, e.CellStyle.Font,
                            Brushes.Crimson, e.CellBounds.X + 2,
                            e.CellBounds.Y + 2, StringFormat.GenericDefault);
                    }
                }

                //下边缘的线
                e.Graphics.DrawLine(gridLinePen, e.CellBounds.Left, e.CellBounds.Bottom - 1,
                                            e.CellBounds.Right - 1, e.CellBounds.Bottom - 1);
                e.Handled = true;
            }
        }

}

#endregion

本文转自 qianshao 51CTO博客，原文链接：http://blog.51cto.com/qianshao/201801，如需转载请自行联系原作者

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