向表单控件添加属性

Question

我已扩展 DataGridView 单元格以在角落显示其 Tag 属性中的文本（例如，在日历的角落显示天数）并希望能够指定文本的颜色和不透明度。

为了实现这一点，我向子类 DataGridView 单元格添加了 2 个属性，但是它们不会在运行时存储它们的值。这是 DataGridViewCell 和 Column：

class DataGridViewLabelCell : DataGridViewTextBoxCell
{
    private Color _textColor;
    private int _opacity;

    public Color TextColor { get { return _textColor; } set { _textColor = value; } }
    public int Opacity { get { return _opacity; } set { _opacity = value; } }

    protected override void Paint(Graphics graphics,
                                  Rectangle clipBounds,
                                  Rectangle cellBounds,
                                  int rowIndex,
                                  DataGridViewElementStates cellState,
                                  object value,
                                  object formattedValue,
                                  string errorText,
                                  DataGridViewCellStyle cellStyle,
                                  DataGridViewAdvancedBorderStyle advancedBorderStyle,
                                  DataGridViewPaintParts paintParts)
    {
        // Call the base class method to paint the default cell appearance.
        base.Paint(graphics, clipBounds, cellBounds, rowIndex, cellState,
            value, formattedValue, errorText, cellStyle,
            advancedBorderStyle, paintParts);

        if (base.Tag != null)
        {
            string tag = base.Tag.ToString();
            Point point = new Point(base.ContentBounds.Location.X, base.ContentBounds.Location.Y);
            Font font = new Font("Arial", 25.0F, FontStyle.Bold);
            graphics.DrawString(tag, font, new SolidBrush(Color.FromArgb(_opacity, _textColor)), cellBounds.X, cellBounds.Y);
        }
    }
}

public class DataGridViewLabelCellColumn : DataGridViewColumn
{
    public DataGridViewLabelCellColumn(Color TextColor, int Opacity = 128)
    {
        DataGridViewLabelCell template = new DataGridViewLabelCell();
        template.TextColor = TextColor;
        template.Opacity = Opacity;
        this.CellTemplate = template;
    }
}

我按如下方式添加列：

col = new DataGridViewLabelCellColumn(Color.Blue, 115);
dgv.Columns.Add(col);
col.HeaderText = "Saturday";
col.Name = "Saturday";

但是，如果我向 graphics.DrawString 行添加断点，_textColor 和 _opacity 都没有值。如果我为它们分配默认值如下：

private Color _textColor = Color.Red;
private int _opacity = 128;

然后它工作正常。如何确保值存储在 CellTemplate 中？

Answer 1

我相信这是因为CellTemplate 存储为更通用的DataGridViewCell，而不是子类LabelCell。无论如何，将值存储在 Column 上并从那里引用它们都可以正常工作：

DataGridViewLabelCellColumn clm = (DataGridViewLabelCellColumn)base.OwningColumn;
int opacity = clm.Opacity;
Color textColor = clm.TextColor;
graphics.DrawString(tag, font, new SolidBrush(Color.FromArgb(opacity, textColor)), cellBounds.X, cellBounds.Y);