BindingSource.MoveFirst 方法 (System.Windows.Forms) | Microsoft Docs

长江黄鹤 2022-02-18

展开全文

移至列表中的第一项。

C＃

public void MoveFirst ();

示例

下面的代码示例演示了 MoveNext 、 MoveFirst 、 Current 和 Position 成员。若要运行此示例，请将代码粘贴到导入命名空间的窗体中，并包含名为的和名为的 System.Drawing.Drawing2D BindingSource BindingSource1 按钮 button1 。将 Form1_Load 和 Form1_Paint 方法与 Load 窗体的和 Paint 事件关联，并将 button1_click 方法与的事件关联 Click button1 。 Visual Basic 用户将需要添加对 System.Data.dll 的引用。

C＃

void Form1_Load(object sender, EventArgs e)
{
    // Set the data source to the Brush type and populate
    // BindingSource1 with some brushes.
    BindingSource1.DataSource = typeof(System.Drawing.Brush);
    BindingSource1.Add(
        new TextureBrush(new Bitmap(typeof(Button), "Button.bmp")));
    BindingSource1.Add(new HatchBrush(HatchStyle.Cross, Color.Red));
    BindingSource1.Add(new SolidBrush(Color.Blue));
}

private void button1_Click(object sender, EventArgs e)
{
    // If you are not at the end of the list, move to the next item
    // in the BindingSource.
    if (BindingSource1.Position + 1 < BindingSource1.Count)
        BindingSource1.MoveNext();

    // Otherwise, move back to the first item.
    else
        BindingSource1.MoveFirst();

    // Force the form to repaint.
    this.Invalidate();
}

void Form1_Paint(object sender, PaintEventArgs e)
{
    // Get the current item in the BindingSource.
    Brush item = (Brush)BindingSource1.Current;

    // If the current type is a TextureBrush, fill an ellipse.
    if (item.GetType() == typeof(TextureBrush))
        e.Graphics.FillEllipse(item,
           e.ClipRectangle);

    // If the current type is a HatchBrush, fill a triangle.
    else if (item.GetType() == typeof(HatchBrush))
        e.Graphics.FillPolygon(item,
            new Point[] { new Point(0, 0), new Point(0, 200),
            new Point(200, 0)});

    // Otherwise, fill a rectangle.
    else
        e.Graphics.FillRectangle(
            (Brush)BindingSource1.Current, e.ClipRectangle);
}