IsBalloon属性使Windows窗体工具提示位置不一致

当我设置ToolTip控件的IsBalloon属性，然后使用ToolTip.Show()方法来显示它时，气球的尾部并不总是指向我请求的位置。似乎我第一次调用Show()时，工具提示控件出现在我要求的位置，其左上角和气球尾部指向下方。如果我在工具提示消失之前再次调用Show()，那么它会重新出现在我要求的位置。

是否有一些设置可以使位置更加一致?如果可能的话，我想保留气球的样式。

下面的代码示例将演示失败。我想让它指向文本框的左上角。

using System;
using System.Windows.Forms;
public class Form1 : Form
{
    const int TIP_X = 50;
    const int TIP_Y = 100;
    private void button1_Click(object sender, EventArgs e)
    {
        toolTip1.Show("Test", groupBox1, TIP_X, TIP_Y, 5000);
    }
    /// <summary>
    /// Required method for Designer support - do not modify
    /// the contents of this method with the code editor.
    /// </summary>
    private void InitializeComponent()
    {
        this.components = new System.ComponentModel.Container();
        this.button1 = new System.Windows.Forms.Button();
        this.groupBox1 = new System.Windows.Forms.GroupBox();
        this.textBox1 = new System.Windows.Forms.TextBox();
        this.toolTip1 = new System.Windows.Forms.ToolTip(this.components);
        this.groupBox1.SuspendLayout();
        this.SuspendLayout();
        this.button1.Location = new System.Drawing.Point(50, 50);
        this.textBox1.Location = new System.Drawing.Point(TIP_X, TIP_Y);
        this.toolTip1.IsBalloon = true;
        this.button1.Click += new System.EventHandler(this.button1_Click);
        this.groupBox1.Controls.Add(this.textBox1);
        this.groupBox1.Controls.Add(this.button1);
        this.groupBox1.Location = new System.Drawing.Point(10, 10);
        this.groupBox1.Size = new System.Drawing.Size(200, 200);
        this.Controls.Add(this.groupBox1);
        this.groupBox1.ResumeLayout(false);
        this.groupBox1.PerformLayout();
        this.ResumeLayout(false);
    }
    public Form1()
    {
        InitializeComponent();
    }
    private Button button1;
    private GroupBox groupBox1;
    private TextBox textBox1;
    private ToolTip toolTip1;
    /// <summary>
    /// Required designer variable.
    /// </summary>
    private System.ComponentModel.IContainer components = null;
    /// <summary>
    /// Clean up any resources being used.
    /// </summary>
    /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
    protected override void Dispose(bool disposing)
    {
        if (disposing && (components != null))
        {
            components.Dispose();
        }
        base.Dispose(disposing);
    }
}

我试图通知用户他们可能感兴趣的东西，但他们可以安全地忽略它。我认为气球通知可以很好地工作，因为它可以指向我正在告诉用户的用户界面中的特定内容。

我用的是Visual Studio 2008，运行在。net 3.5和windows XP下。

    private void button1_Click(object sender, EventArgs e)
    {
        toolTip1.Show("Test", groupBox1, TIP_X, TIP_Y, 5000);
        toolTip1.Show("Test", groupBox1, TIP_X, TIP_Y, 5000);
    }