从一个Listbox 里拖拽 数据到 TextBox，为什么TextBox的DragDrop事件无法触发？？

Question

在From内放了 两个控件  TextBox 和Listbox
在Listbox内增加了几行数据设置TextBox  AllowDrop＝True代码如下
private void listBox1_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
{
// Determines which item was selected.
string a;
ListBox lb =( (ListBox)sender);
Point pt = new Point(e.X,e.Y);
int index = lb.IndexFromPoint(pt); // Starts a drag-and-drop operation with that item.
if(index>=0) 
{
lb.DoDragDrop(lb.Items[index].ToString(), DragDropEffects.Link);
a = lb.Items[index].ToString();
} }
private void textBox1_DragEnter(object sender, System.Windows.Forms.DragEventArgs e)
{
// If the data is text, copy the data to the RichTextBox control.
if(e.Data.GetDataPresent("Text"))
e.Effect = DragDropEffects.Copy; }
private void textBox1_DragDrop(object sender, System.Windows.Forms.DragEventArgs e)
{
// Loads the file into the control. 
//richTextBox1.LoadFile((String)e.Data.GetData("Text"), System.Windows.Forms.RichTextBoxStreamType.RichText);
textBox1.Text = (String)e.Data.GetData("Text");
}
this.textBox1.DragDrop += new System.Windows.Forms.DragEventHandler(this.textBox1_DragDrop);
this.textBox1.DragEnter += new System.Windows.Forms.DragEventHandler(this.textBox1_DragEnter);
结果时 Drag的数据可以看到 就是 DragDrop 无法触发  
请高手指点！！！ 急！！

Answer 1

设置TextBox的AllowDrop属性为true.

Answer 2

这恐怕还不行吧，DoDragDrop至少应该写在listbox的mousemove事件里

Answer 3

.net framework里面不是有一个现成的例子吗？using System;
using System.Data;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;namespace CS_Test2005_07_07
{
/// <summary>
/// Form6 的摘要说明。
/// </summary>
public class Form6 : System.Windows.Forms.Form
{
        private System.Windows.Forms.TextBox textBox1;
        private System.Windows.Forms.ListBox ListDragTarget;
        private System.Windows.Forms.Label DropLocationLabel;
        private System.Windows.Forms.ListBox ListDragSource;
        private System.Windows.Forms.CheckBox UseCustomCursorsCheck;
        private System.ComponentModel.IContainer components = null; public Form6()
{
//
// Windows 窗体设计器支持所必需的
//
InitializeComponent(); //
// TODO: 在 InitializeComponent 调用后添加任何构造函数代码
//
} /// <summary>
/// 清理所有正在使用的资源。
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
if(components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
} #region Windows 窗体设计器生成的代码
/// <summary>
/// 设计器支持所需的方法 - 不要使用代码编辑器修改
/// 此方法的内容。
/// </summary>
private void InitializeComponent()
{
            this.textBox1 = new System.Windows.Forms.TextBox();
            this.ListDragTarget = new System.Windows.Forms.ListBox();
            this.DropLocationLabel = new System.Windows.Forms.Label();
            this.ListDragSource = new System.Windows.Forms.ListBox();
            this.UseCustomCursorsCheck = new System.Windows.Forms.CheckBox();
            this.SuspendLayout();
            // 
            // textBox1
            // 
            this.textBox1.AllowDrop = true;
            this.textBox1.Location = new System.Drawing.Point(304, 16);
            this.textBox1.Name = "textBox1";
            this.textBox1.Size = new System.Drawing.Size(192, 21);
            this.textBox1.TabIndex = 0;
            this.textBox1.Text = "textBox1";
            // 
            // ListDragTarget
            // 
            this.ListDragTarget.AllowDrop = true;
            this.ListDragTarget.ItemHeight = 12;
            this.ListDragTarget.Items.AddRange(new object[] {
                                                                "efaweg",
                                                                "wegaweg",
                                                                "erwahger",
                                                                "rewagreg"});
            this.ListDragTarget.Location = new System.Drawing.Point(80, 112);
            this.ListDragTarget.Name = "ListDragTarget";
            this.ListDragTarget.Size = new System.Drawing.Size(120, 88);
            this.ListDragTarget.TabIndex = 1;
            this.ListDragTarget.DragOver += new System.Windows.Forms.DragEventHandler(this.ListDragTarget_DragOver);
            this.ListDragTarget.DragDrop += new System.Windows.Forms.DragEventHandler(this.ListDragTarget_DragDrop);
            this.ListDragTarget.DragEnter += new System.Windows.Forms.DragEventHandler(this.ListDragTarget_DragEnter);
            this.ListDragTarget.DragLeave += new System.EventHandler(this.ListDragTarget_DragLeave);
            // 
            // DropLocationLabel
            // 
            this.DropLocationLabel.Location = new System.Drawing.Point(176, 16);
            this.DropLocationLabel.Name = "DropLocationLabel";
            this.DropLocationLabel.TabIndex = 2;
            this.DropLocationLabel.Text = "label1";
            // 
            // ListDragSource
            // 
            this.ListDragSource.ItemHeight = 12;
            this.ListDragSource.Items.AddRange(new object[] {
                                                                "GBWEWE",
                                                                "HGEWG",
                                                                "RWEG"});
            this.ListDragSource.Location = new System.Drawing.Point(288, 112);
            this.ListDragSource.Name = "ListDragSource";
            this.ListDragSource.Size = new System.Drawing.Size(120, 88);
            this.ListDragSource.TabIndex = 3;
            this.ListDragSource.MouseDown += new System.Windows.Forms.MouseEventHandler(this.ListDragSource_MouseDown);
            this.ListDragSource.QueryContinueDrag += new System.Windows.Forms.QueryContinueDragEventHandler(this.ListDragSource_QueryContinueDrag);
            this.ListDragSource.MouseUp += new System.Windows.Forms.MouseEventHandler(this.ListDragSource_MouseUp);
            this.ListDragSource.MouseMove += new System.Windows.Forms.MouseEventHandler(this.ListDragSource_MouseMove);
            this.ListDragSource.GiveFeedback += new System.Windows.Forms.GiveFeedbackEventHandler(this.ListDragSource_GiveFeedback);
            // 
            // UseCustomCursorsCheck
            // 
            this.UseCustomCursorsCheck.Location = new System.Drawing.Point(168, 64);
            this.UseCustomCursorsCheck.Name = "UseCustomCursorsCheck";
            this.UseCustomCursorsCheck.TabIndex = 4;
            this.UseCustomCursorsCheck.Text = "checkBox1";
            // 
            // Form6
            // 
            this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
            this.ClientSize = new System.Drawing.Size(704, 365);
            this.Controls.Add(this.UseCustomCursorsCheck);
            this.Controls.Add(this.ListDragSource);
            this.Controls.Add(this.DropLocationLabel);
            this.Controls.Add(this.ListDragTarget);
            this.Controls.Add(this.textBox1);
            this.Name = "Form6";
            this.Text = "Form6";
            this.Load += new System.EventHandler(this.Form6_Load);
            this.ResumeLayout(false);        }
#endregion        private int indexOfItemUnderMouseToDrag;
        private int indexOfItemUnderMouseToDrop;        
        
        private Rectangle dragBoxFromMouseDown;
        private Point screenOffset;        private Cursor MyNoDropCursor;
        private Cursor MyNormalCursor;        private void Form6_Load(object sender, System.EventArgs e)
        {
            
        }       
        private void ListDragSource_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
        {
            // Get the index of the item the mouse is below.
            indexOfItemUnderMouseToDrag = ListDragSource.IndexFromPoint(e.X, e.Y);            if (indexOfItemUnderMouseToDrag != ListBox.NoMatches) 
            {
                                
                // Remember the point where the mouse down occurred. The DragSize indicates
                // the size that the mouse can move before a drag event should be started.                
                Size dragSize = SystemInformation.DragSize;                // Create a rectangle using the DragSize, with the mouse position being
                // at the center of the rectangle.
                dragBoxFromMouseDown = new Rectangle(new Point(e.X - (dragSize.Width /2),
                    e.Y - (dragSize.Height /2)), dragSize);
            } 
            else
                // Reset the rectangle if the mouse is not over an item in the ListBox.
                dragBoxFromMouseDown = Rectangle.Empty;        }        private void ListDragSource_MouseUp(object sender, System.Windows.Forms.MouseEventArgs e)
        {
            // Reset the drag rectangle when the mouse button is raised.
            dragBoxFromMouseDown = Rectangle.Empty;        }

Answer 4

private void ListDragSource_MouseMove(object sender, System.Windows.Forms.MouseEventArgs e)
        {
            if ((e.Button & MouseButtons.Left) == MouseButtons.Left) 
            {                // If the mouse moves outside the rectangle, start the drag.
                if (dragBoxFromMouseDown != Rectangle.Empty && 
                    !dragBoxFromMouseDown.Contains(e.X, e.Y)) 
                {                    // Create custom cursors for the drag-and-drop operation.
                    try 
                    {
                        MyNormalCursor = new Cursor("3dwarro.cur");
                        MyNoDropCursor = new Cursor("3dwno.cur");                    } 
                    catch 
                    {
                        // An error occurred while attempting to load the cursors, so use
                        // standard cursors.
                        UseCustomCursorsCheck.Checked = false;
                    }
                    finally 
                    {                        // The screenOffset is used to account for any desktop bands 
                        // that may be at the top or left side of the screen when 
                        // determining when to cancel the drag drop operation.
                        screenOffset = SystemInformation.WorkingArea.Location;                        // Proceed with the drag and drop, passing in the list item.                    
                        DragDropEffects dropEffect = ListDragSource.DoDragDrop(ListDragSource.Items[indexOfItemUnderMouseToDrag], DragDropEffects.All | DragDropEffects.Link);                        // If the drag operation was a move then remove the item.
                        if (dropEffect == DragDropEffects.Move) 
                        {                        
                            ListDragSource.Items.RemoveAt(indexOfItemUnderMouseToDrag);                            // Selects the previous item in the list as long as the list has an item.
                            if (indexOfItemUnderMouseToDrag > 0)
                                ListDragSource.SelectedIndex = indexOfItemUnderMouseToDrag -1;                            else if (ListDragSource.Items.Count > 0)
                                // Selects the first item.
                                ListDragSource.SelectedIndex =0;
                        }                        // Dispose of the cursors since they are no longer needed.
                        if (MyNormalCursor != null)
                            MyNormalCursor.Dispose();                        if (MyNoDropCursor != null)
                            MyNoDropCursor.Dispose();
                    }
                }
            }        }        private void ListDragSource_GiveFeedback(object sender, System.Windows.Forms.GiveFeedbackEventArgs e)
        {
            // Use custom cursors if the check box is checked.
            if (UseCustomCursorsCheck.Checked) 
            {                // Sets the custom cursor based upon the effect.
                e.UseDefaultCursors = false;
                if ((e.Effect & DragDropEffects.Move) == DragDropEffects.Move)
                    Cursor.Current = MyNormalCursor;
                else 
                    Cursor.Current = MyNoDropCursor;
            }        }

Answer 5

        private void ListDragTarget_DragOver(object sender, System.Windows.Forms.DragEventArgs e)
        {
            // Determine whether string data exists in the drop data. If not, then
            // the drop effect reflects that the drop cannot occur.
            if (!e.Data.GetDataPresent(typeof(System.String))) 
            {                e.Effect = DragDropEffects.None;
                DropLocationLabel.Text = "None - no string data.";
                return;
            }            // Set the effect based upon the KeyState.
            if ((e.KeyState & (8+32)) == (8+32) && 
                (e.AllowedEffect & DragDropEffects.Link) == DragDropEffects.Link) 
            {
                // KeyState 8 + 32 = CTL + ALT                // Link drag and drop effect.
                e.Effect = DragDropEffects.Link;            } 
            else if ((e.KeyState & 32) == 32 && 
                (e.AllowedEffect & DragDropEffects.Link) == DragDropEffects.Link) 
            {                // ALT KeyState for link.
                e.Effect = DragDropEffects.Link;            } 
            else if ((e.KeyState & 4) == 4 && 
                (e.AllowedEffect & DragDropEffects.Move) == DragDropEffects.Move) 
            {                // SHIFT KeyState for move.
                e.Effect = DragDropEffects.Move;            } 
            else if ((e.KeyState & 8) == 8 && 
                (e.AllowedEffect & DragDropEffects.Copy) == DragDropEffects.Copy) 
            {                // CTL KeyState for copy.
                e.Effect = DragDropEffects.Copy;            } 
            else if ((e.AllowedEffect & DragDropEffects.Move) == DragDropEffects.Move)  
            {                // By default, the drop action should be move, if allowed.
                e.Effect = DragDropEffects.Move;            } 
            else
                e.Effect = DragDropEffects.None;
                
            // Get the index of the item the mouse is below.             // The mouse locations are relative to the screen, so they must be 
            // converted to client coordinates.            indexOfItemUnderMouseToDrop = 
                ListDragTarget.IndexFromPoint(ListDragTarget.PointToClient(new Point(e.X, e.Y)));            // Updates the label text.
            if (indexOfItemUnderMouseToDrop != ListBox.NoMatches)
            {                DropLocationLabel.Text = "Drops before item #" + (indexOfItemUnderMouseToDrop + 1);
            } 
            else
                DropLocationLabel.Text = "Drops at the end.";        }
        private void ListDragTarget_DragDrop(object sender, System.Windows.Forms.DragEventArgs e)
        {
            // Ensure that the list item index is contained in the data.
            if (e.Data.GetDataPresent(typeof(System.String))) 
            {                Object item = (object)e.Data.GetData(typeof(System.String));                // Perform drag and drop, depending upon the effect.
                if (e.Effect == DragDropEffects.Copy ||
                    e.Effect == DragDropEffects.Move) 
                {
        
                    // Insert the item.
                    if (indexOfItemUnderMouseToDrop != ListBox.NoMatches)
                        ListDragTarget.Items.Insert(indexOfItemUnderMouseToDrop, item);
                    else
                        ListDragTarget.Items.Add(item);
            
                }
            }
            // Reset the label text.
            DropLocationLabel.Text = "None";        }        private void ListDragSource_QueryContinueDrag(object sender, System.Windows.Forms.QueryContinueDragEventArgs e)
        {
            // Cancel the drag if the mouse moves off the form.
            ListBox lb = sender as ListBox;            if (lb != null) 
            {                Form f = lb.FindForm();                // Cancel the drag if the mouse moves off the form. The screenOffset
                // takes into account any desktop bands that may be at the top or left
                // side of the screen.
                if (((Control.MousePosition.X - screenOffset.X) < f.DesktopBounds.Left) ||
                    ((Control.MousePosition.X - screenOffset.X) > f.DesktopBounds.Right) ||
                    ((Control.MousePosition.Y - screenOffset.Y) < f.DesktopBounds.Top) ||
                    ((Control.MousePosition.Y - screenOffset.Y) > f.DesktopBounds.Bottom)) 
                {                    e.Action = DragAction.Cancel;
                }
            }        }        private void ListDragTarget_DragEnter(object sender, System.Windows.Forms.DragEventArgs e)
        {
            // Reset the label text.
            DropLocationLabel.Text = "None";        }        private void ListDragTarget_DragLeave(object sender, System.EventArgs e)
        {
            // Reset the label text.
            DropLocationLabel.Text = "None";        }       
    }
}