在多级下拉列表中将ToolStripDropDown.DropShadowEnabled设置为false

Question

我想禁用ToolStripDropDownButton下拉列表上的下拉阴影。如果下拉菜单包含具有下拉菜单本身的项目(例如多级菜单)，则在ToolStripDropDownButton上将DropShadowEnabled设置为false会导致顶级下拉菜单出现在错误的位置。请参阅附件中的图片。

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public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        toolStripDropDownButton1.DropDown.DropShadowEnabled = false;
    }
}


partial class Form1
{
    /// <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);
    }

    #region Windows Form Designer generated code

    /// <summary>
    /// Required method for Designer support - do not modify
    /// the contents of this method with the code editor.
    /// </summary>
    private void InitializeComponent()
    {
        System.ComponentModel.ComponentResourceManager resources = new System.ComponentModel.ComponentResourceManager(typeof(Form1));
        this.toolStrip1 = new System.Windows.Forms.ToolStrip();
        this.toolStripDropDownButton1 = new System.Windows.Forms.ToolStripDropDownButton();
        this.item1ToolStripMenuItem = new System.Windows.Forms.ToolStripMenuItem();
        this.subitem1ToolStripMenuItem = new System.Windows.Forms.ToolStripMenuItem();
        this.toolStrip1.SuspendLayout();
        this.SuspendLayout();
        // 
        // toolStrip1
        // 
        this.toolStrip1.Items.AddRange(new System.Windows.Forms.ToolStripItem[] {
        this.toolStripDropDownButton1});
        this.toolStrip1.Location = new System.Drawing.Point(0, 0);
        this.toolStrip1.Name = "toolStrip1";
        this.toolStrip1.Size = new System.Drawing.Size(292, 25);
        this.toolStrip1.TabIndex = 0;
        this.toolStrip1.Text = "toolStrip1";
        // 
        // toolStripDropDownButton1
        // 
        this.toolStripDropDownButton1.DisplayStyle = System.Windows.Forms.ToolStripItemDisplayStyle.Image;
        this.toolStripDropDownButton1.DropDownItems.AddRange(new System.Windows.Forms.ToolStripItem[] {
        this.item1ToolStripMenuItem});
        this.toolStripDropDownButton1.Image = ((System.Drawing.Image)(resources.GetObject("toolStripDropDownButton1.Image")));
        this.toolStripDropDownButton1.ImageTransparentColor = System.Drawing.Color.Magenta;
        this.toolStripDropDownButton1.Name = "toolStripDropDownButton1";
        this.toolStripDropDownButton1.Size = new System.Drawing.Size(29, 22);
        this.toolStripDropDownButton1.Text = "toolStripDropDownButton1";
        // 
        // item1ToolStripMenuItem
        // 
        this.item1ToolStripMenuItem.DropDownItems.AddRange(new System.Windows.Forms.ToolStripItem[] {
        this.subitem1ToolStripMenuItem});
        this.item1ToolStripMenuItem.Name = "item1ToolStripMenuItem";
        this.item1ToolStripMenuItem.Size = new System.Drawing.Size(152, 22);
        this.item1ToolStripMenuItem.Text = "item1";
        // 
        // subitem1ToolStripMenuItem
        // 
        this.subitem1ToolStripMenuItem.Name = "subitem1ToolStripMenuItem";
        this.subitem1ToolStripMenuItem.Size = new System.Drawing.Size(152, 22);
        this.subitem1ToolStripMenuItem.Text = "subitem1";
        // 
        // Form1
        // 
        this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
        this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
        this.ClientSize = new System.Drawing.Size(292, 273);
        this.Controls.Add(this.toolStrip1);
        this.Name = "Form1";
        this.Text = "Form1";
        this.toolStrip1.ResumeLayout(false);
        this.toolStrip1.PerformLayout();
        this.ResumeLayout(false);
        this.PerformLayout();

    }

    #endregion

    private System.Windows.Forms.ToolStrip toolStrip1;
    private System.Windows.Forms.ToolStripDropDownButton toolStripDropDownButton1;
    private System.Windows.Forms.ToolStripMenuItem item1ToolStripMenuItem;
    private System.Windows.Forms.ToolStripMenuItem subitem1ToolStripMenuItem;
}

Answer 1

这是ToolStripItem类中非常典型的损失。很明显，这是一个bug，可能是当他们应用黑客来解决Windows问题时引入的。您仍然可以在Reference Source中看到内部错误号：

public bool DropShadowEnabled {
    get {
        // VSWhidbey 338272 - DropShadows are only supported on TopMost windows
        // due to the flakeyness of the way it's implemented in the OS. (Non toplevel
        // windows can have parts of the shadow disappear because another window can get
        // sandwiched between the SysShadow window and the dropdown.)
        return dropShadowEnabled && TopMost && DisplayInformation.IsDropShadowEnabled;
    }
    set {  // etc... }
}

但是在设置器和呈现器中没有相应的修复。

他们提到的缺陷实际上已经在Vista中修复了，你仍然在XP上运行，所以你看不到它。投影在Aero桌面上的处理方式不同，无论是否启用，都是系统设置。所以在Aero上使用该属性是完全无效的。

在WinForms2.0发布后，这些ToolStripItem类错误没有得到修复，大约整个.NET团队都转移到了WPF组。而且它们现在肯定不会得到修复，没有必要在connect.microsoft.com上提交错误，尽管您可以自由地这样做。

由于该属性现在是系统设置，因此无法再对Windows的后续版本产生影响，因此唯一符合逻辑的做法就是认输。不要更改该属性。