C# ListBox.ScrollAlwaysVisible属性代码示例

internal System.Windows.Forms.ListBox ListBox1;

private void InitializeOwnerDrawnListBox()
{
    this.ListBox1 = new System.Windows.Forms.ListBox();

    // Set the location and size.
    ListBox1.Location = new Point(20, 20);
    ListBox1.Size = new Size(240, 240);

    // Populate the ListBox.ObjectCollection property 
    // with several strings, using the AddRange method.
    this.ListBox1.Items.AddRange(new object[]{"System.Windows.Forms", 
        "System.Drawing", "System.Xml", "System.Net", "System.Runtime.Remoting", 
        "System.Web"});

    // Turn off the scrollbar.
    ListBox1.ScrollAlwaysVisible = false;

    // Set the border style to a single, flat border.
    ListBox1.BorderStyle = BorderStyle.FixedSingle;

    // Set the DrawMode property to the OwnerDrawVariable value. 
    // This means the MeasureItem and DrawItem events must be 
    // handled.
    ListBox1.DrawMode = DrawMode.OwnerDrawVariable;
    ListBox1.MeasureItem += 
        new MeasureItemEventHandler(ListBox1_MeasureItem);
    ListBox1.DrawItem += new DrawItemEventHandler(ListBox1_DrawItem);
    this.Controls.Add(this.ListBox1);
}

// Handle the DrawItem event for an owner-drawn ListBox.
private void ListBox1_DrawItem(object sender, DrawItemEventArgs e)
{

    // If the item is the selected item, then draw the rectangle
    // filled in blue. The item is selected when a bitwise And  
    // of the State property and the DrawItemState.Selected 
    // property is true.
    if ((e.State & DrawItemState.Selected) == DrawItemState.Selected)
    {
        e.Graphics.FillRectangle(Brushes.CornflowerBlue, e.Bounds);
    }
    else
    {
        // Otherwise, draw the rectangle filled in beige.
        e.Graphics.FillRectangle(Brushes.Beige, e.Bounds);
    }

    // Draw a rectangle in blue around each item.
    e.Graphics.DrawRectangle(Pens.Blue, e.Bounds);

    // Draw the text in the item.
    e.Graphics.DrawString(ListBox1.Items[e.Index].ToString(),
        this.Font, Brushes.Black, e.Bounds.X, e.Bounds.Y);

    // Draw the focus rectangle around the selected item.
    e.DrawFocusRectangle();
}

// Handle the MeasureItem event for an owner-drawn ListBox.
private void ListBox1_MeasureItem(object sender, 
    MeasureItemEventArgs e)
{

    // Cast the sender object back to ListBox type.
    ListBox theListBox = (ListBox) sender;

    // Get the string contained in each item.
    string itemString = (string) theListBox.Items[e.Index];

    // Split the string at the " . "  character.
    string[] resultStrings = itemString.Split('.');

    // If the string contains more than one period, increase the 
    // height by ten pixels; otherwise, increase the height by 
    // five pixels.
    if (resultStrings.Length>2)
    {
        e.ItemHeight += 10;
    }
    else
    {
        e.ItemHeight += 5;
    }
}

//引入命名空间
using System;
using System.Drawing;
using System.Windows.Forms;
using System.Data;
using System.Data.SqlClient;

public class ListBoxSelectionMode : Form
{
  ListBox lb;
  RadioButton rdoMultiExtended;
  RadioButton rdoMultiSimple;
  RadioButton rdoMultiOne;
  TextBox txtTop;
  Button btnTop;

  public ListBoxSelectionMode()
  {
    int xSize, ySize;

    Size = new Size(300,400);

    lb = new ListBox();
    lb.Parent = this;
    lb.Location = new Point(10,10);
    lb.Size = new Size(ClientSize.Width - 20, Height - 200);
    lb.Anchor = AnchorStyles.Top | AnchorStyles.Left | AnchorStyles.Right | AnchorStyles.Bottom;
    lb.BorderStyle = BorderStyle.Fixed3D;
    lb.MultiColumn = true;
    lb.ScrollAlwaysVisible = true;

    GroupBox grpMulti = new GroupBox();
    grpMulti.Parent = this;
    grpMulti.Text = "MultiSelect";
    grpMulti.Location = new Point(lb.Left, lb.Bottom + 25);
    grpMulti.Anchor = AnchorStyles.Left | AnchorStyles.Bottom;

    rdoMultiOne = new RadioButton();
    rdoMultiOne.Parent = grpMulti;
    rdoMultiOne.Text = "One";
    rdoMultiOne.Tag = SelectionMode.One;
    rdoMultiOne.Checked = true;
    rdoMultiOne.Location = new Point(10,15);
    rdoMultiOne.CheckedChanged += new System.EventHandler(rdoMulti_CheckedChanged);

    rdoMultiSimple = new RadioButton();
    rdoMultiSimple.Parent = grpMulti;
    rdoMultiSimple.Text = "Multi-Simple";
    rdoMultiSimple.Tag = SelectionMode.MultiSimple;
    rdoMultiSimple.Location = new Point(10, rdoMultiOne.Bottom);
    rdoMultiSimple.CheckedChanged += new System.EventHandler(rdoMulti_CheckedChanged);

    rdoMultiExtended = new RadioButton();
    rdoMultiExtended.Parent = grpMulti;
    rdoMultiExtended.Text = "Multi-Extended";
    rdoMultiExtended.Tag = SelectionMode.MultiExtended;
    rdoMultiExtended.Location = new Point(10, rdoMultiSimple.Bottom);
    rdoMultiExtended.CheckedChanged += new System.EventHandler(rdoMulti_CheckedChanged);

    xSize = (int)(Font.Height * .75) * rdoMultiExtended.Text.Length;
    ySize = ((int)rdoMultiOne.Height * 3) + 20;
    grpMulti.Size = new Size(xSize, ySize);

    Panel pnlTop = new Panel();
    pnlTop.Parent = this;
    pnlTop.Location = new Point(lb.Left, grpMulti.Bottom + 10);
    pnlTop.Anchor = AnchorStyles.Left | AnchorStyles.Bottom;

    Label lblTop = new Label();
    lblTop.Parent = pnlTop;
    lblTop.Text = "TopIndex: ";
    xSize = ((int)(Font.Height * .5) * lblTop.Text.Length);
    lblTop.Size = new Size(xSize, Font.Height + 10);

    txtTop = new TextBox();
    txtTop.Parent = pnlTop;
    txtTop.Location = new Point(lblTop.Right, lblTop.Top);
    txtTop.Text = lb.TopIndex.ToString();
    txtTop.Size = new Size((int)(Font.Height * .75) * 3, 
                Font.Height + 10);

    btnTop = new Button();
    btnTop.Parent = pnlTop;
    btnTop.Text = "Update";
    btnTop.Location = new Point(txtTop.Right + 10, txtTop.Top);
    btnTop.Click += new System.EventHandler(btnTop_Click);


    lb.Items.Add("12345");
      lb.Items.Add("67890");      
      lb.Items.Add("7890");      
      lb.Items.Add("890");            
  } 

  static void Main() 
  {
    Application.Run(new ListBoxSelectionMode());
  }

  private void rdoMulti_CheckedChanged(object sender, EventArgs e)
  {
    RadioButton rdo = (RadioButton)sender;
    lb.SelectionMode = (SelectionMode)rdo.Tag;
  }

  private void btnTop_Click(object sender, EventArgs e)
  {
    txtTop.Text = lb.TopIndex.ToString();
  }
}