C# 是什么导致这种不一致的枚举？在加载处理程序中使用LINQ与foreach访问UltraGroupBox的控件

当使用顶部答案中的GetAll方法递归获取表单上的所有组合框时，如果组合框位于UltraGroupBox中，则结果的行为会异常。在使用LINQ和foreach处理返回的IEnumerable时，我得到了不一致的结果。请参阅下面的独立程序示例，为您自己重现问题。以下代码片段举例说明了该问题：

var combos = GetAll(this, typeof(ComboBox)).Cast<ComboBox>();

var linqNames = combos.Select(c => c.Name).ToList();
var foreachNames = new List<string>();

foreach (var comboBox in combos)
{
    foreachNames.Add(comboBox.Name);
}

Debug.WriteLine(String.Join(", ", linqNames));
Debug.WriteLine(String.Join(", ", foreachNames));

请注意，foreach结果中缺少cbo2、cbo4和cbo6。这是在表单的加载事件处理程序中执行的。组合框都位于同一Infrastics UltraGroupBox中。是什么导致了这种奇怪的行为？UltraGroupBox的控件属性是否有副作用

编辑：我意识到如下将ToList添加到GetAll的返回中会导致结果匹配，但我想知道为什么仅使用IEnumerable时枚举不一致

var combos = GetAll(this, typeof(ComboBox)).Cast<ComboBox>().ToList();

编辑2：以下是使用.NET 4.0和Infragistics NetAdvantage 2013.1程序集的独立程序的设计器代码：

namespace WindowsFormsApplication2
{
    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 Component 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()
    {
        Infragistics.Win.Appearance appearance1 = new Infragistics.Win.Appearance();
        this.grpTest = new Infragistics.Win.Misc.UltraGroupBox();
        this.label20 = new System.Windows.Forms.Label();
        this.label18 = new System.Windows.Forms.Label();
        this.label14 = new System.Windows.Forms.Label();
        this.label5 = new System.Windows.Forms.Label();
        this.label4 = new System.Windows.Forms.Label();
        this.label3 = new System.Windows.Forms.Label();
        this.cbo4 = new System.Windows.Forms.ComboBox();
        this.cbo6 = new System.Windows.Forms.ComboBox();
        this.cbo5 = new System.Windows.Forms.ComboBox();
        this.cbo2 = new System.Windows.Forms.ComboBox();
        this.cbo3 = new System.Windows.Forms.ComboBox();
        this.cbo1 = new System.Windows.Forms.ComboBox();
        ((System.ComponentModel.ISupportInitialize)(this.grpTest)).BeginInit();
        this.grpTest.SuspendLayout();
        this.SuspendLayout();
        // 
        // grpTest
        // 
        this.grpTest.BorderStyle = Infragistics.Win.Misc.GroupBoxBorderStyle.None;
        this.grpTest.Controls.Add(this.label20);
        this.grpTest.Controls.Add(this.label18);
        this.grpTest.Controls.Add(this.label14);
        this.grpTest.Controls.Add(this.label5);
        this.grpTest.Controls.Add(this.label4);
        this.grpTest.Controls.Add(this.label3);
        this.grpTest.Controls.Add(this.cbo4);
        this.grpTest.Controls.Add(this.cbo6);
        this.grpTest.Controls.Add(this.cbo5);
        this.grpTest.Controls.Add(this.cbo2);
        this.grpTest.Controls.Add(this.cbo3);
        this.grpTest.Controls.Add(this.cbo1);
        this.grpTest.Dock = System.Windows.Forms.DockStyle.Top;
        appearance1.BackColor = System.Drawing.Color.DimGray;
        appearance1.BackColor2 = System.Drawing.Color.DimGray;
        appearance1.FontData.BoldAsString = "True";
        appearance1.FontData.SizeInPoints = 10F;
        appearance1.ForeColor = System.Drawing.Color.White;
        this.grpTest.HeaderAppearance = appearance1;
        this.grpTest.Location = new System.Drawing.Point(0, 0);
        this.grpTest.Name = "grpTest";
        this.grpTest.Size = new System.Drawing.Size(463, 261);
        this.grpTest.TabIndex = 13;
        this.grpTest.Text = "Test";
        // 
        // label20
        // 
        this.label20.AutoSize = true;
        this.label20.Location = new System.Drawing.Point(135, 180);
        this.label20.Name = "label20";
        this.label20.Size = new System.Drawing.Size(49, 13);
        this.label20.TabIndex = 25;
        this.label20.Text = "Combo 6";
        // 
        // label18
        // 
        this.label18.AutoSize = true;
        this.label18.Location = new System.Drawing.Point(134, 158);
        this.label18.Name = "label18";
        this.label18.Size = new System.Drawing.Size(49, 13);
        this.label18.TabIndex = 24;
        this.label18.Text = "Combo 5";
        // 
        // label14
        // 
        this.label14.AutoSize = true;
        this.label14.Location = new System.Drawing.Point(133, 136);
        this.label14.Name = "label14";
        this.label14.Size = new System.Drawing.Size(49, 13);
        this.label14.TabIndex = 23;
        this.label14.Text = "Combo 4";
        // 
        // label5
        // 
        this.label5.AutoSize = true;
        this.label5.Location = new System.Drawing.Point(134, 114);
        this.label5.Name = "label5";
        this.label5.Size = new System.Drawing.Size(49, 13);
        this.label5.TabIndex = 22;
        this.label5.Text = "Combo 3";
        // 
        // label4
        // 
        this.label4.AutoSize = true;
        this.label4.Location = new System.Drawing.Point(134, 92);
        this.label4.Name = "label4";
        this.label4.Size = new System.Drawing.Size(49, 13);
        this.label4.TabIndex = 21;
        this.label4.Text = "Combo 2";
        // 
        // label3
        // 
        this.label3.AutoSize = true;
        this.label3.Location = new System.Drawing.Point(134, 70);
        this.label3.Name = "label3";
        this.label3.Size = new System.Drawing.Size(49, 13);
        this.label3.TabIndex = 20;
        this.label3.Text = "Combo 1";
        // 
        // cbo4
        // 
        this.cbo4.FlatStyle = System.Windows.Forms.FlatStyle.Popup;
        this.cbo4.FormattingEnabled = true;
        this.cbo4.Items.AddRange(new object[] {
        "A",
        "B"});
        this.cbo4.Location = new System.Drawing.Point(190, 133);
        this.cbo4.Name = "cbo4";
        this.cbo4.Size = new System.Drawing.Size(121, 21);
        this.cbo4.TabIndex = 7;
        // 
        // cbo6
        // 
        this.cbo6.FlatStyle = System.Windows.Forms.FlatStyle.Popup;
        this.cbo6.FormattingEnabled = true;
        this.cbo6.Items.AddRange(new object[] {
        "A",
        "B"});
        this.cbo6.Location = new System.Drawing.Point(190, 177);
        this.cbo6.Name = "cbo6";
        this.cbo6.Size = new System.Drawing.Size(121, 21);
        this.cbo6.TabIndex = 11;
        // 
        // cbo5
        // 
        this.cbo5.FlatStyle = System.Windows.Forms.FlatStyle.Popup;
        this.cbo5.FormattingEnabled = true;
        this.cbo5.Items.AddRange(new object[] {
        "A",
        "B",
        "C"});
        this.cbo5.Location = new System.Drawing.Point(190, 155);
        this.cbo5.Name = "cbo5";
        this.cbo5.Size = new System.Drawing.Size(121, 21);
        this.cbo5.TabIndex = 9;
        // 
        // cbo2
        // 
        this.cbo2.FlatStyle = System.Windows.Forms.FlatStyle.Popup;
        this.cbo2.FormattingEnabled = true;
        this.cbo2.Items.AddRange(new object[] {
        "A",
        "B",
        "C"});
        this.cbo2.Location = new System.Drawing.Point(190, 89);
        this.cbo2.Name = "cbo2";
        this.cbo2.Size = new System.Drawing.Size(121, 21);
        this.cbo2.TabIndex = 4;
        // 
        // cbo3
        // 
        this.cbo3.FlatStyle = System.Windows.Forms.FlatStyle.Popup;
        this.cbo3.FormattingEnabled = true;
        this.cbo3.Items.AddRange(new object[] {
        "A",
        "B"});
        this.cbo3.Location = new System.Drawing.Point(190, 111);
        this.cbo3.Name = "cbo3";
        this.cbo3.Size = new System.Drawing.Size(121, 21);
        this.cbo3.TabIndex = 5;
        // 
        // cbo1
        // 
        this.cbo1.FlatStyle = System.Windows.Forms.FlatStyle.Popup;
        this.cbo1.FormattingEnabled = true;
        this.cbo1.Items.AddRange(new object[] {
        "A",
        "B",
        "C"});
        this.cbo1.Location = new System.Drawing.Point(190, 67);
        this.cbo1.Name = "cbo1";
        this.cbo1.Size = new System.Drawing.Size(121, 21);
        this.cbo1.TabIndex = 3;
        // 
        // Form1
        // 
        this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
        this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
        this.ClientSize = new System.Drawing.Size(463, 277);
        this.Controls.Add(this.grpTest);
        this.Name = "Form1";
        this.Load += new System.EventHandler(this.Form1_Load);
        ((System.ComponentModel.ISupportInitialize)(this.grpTest)).EndInit();
        this.grpTest.ResumeLayout(false);
        this.grpTest.PerformLayout();
        this.ResumeLayout(false);

    }

    #endregion

    private Infragistics.Win.Misc.UltraGroupBox grpTest;
    private System.Windows.Forms.ComboBox cbo3;
    private System.Windows.Forms.ComboBox cbo2;
    private System.Windows.Forms.ComboBox cbo1;
    private System.Windows.Forms.Label label20;
    private System.Windows.Forms.Label label18;
    private System.Windows.Forms.Label label14;
    private System.Windows.Forms.Label label5;
    private System.Windows.Forms.Label label4;
    private System.Windows.Forms.Label label3;
    private System.Windows.Forms.ComboBox cbo6;
    private System.Windows.Forms.ComboBox cbo5;
    private System.Windows.Forms.ComboBox cbo4;
}
}

以及主实现文件：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Windows.Forms;


namespace WindowsFormsApplication2
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            if (!DesignMode)
            {
                var combos = GetAll(this, typeof(ComboBox)).Cast<ComboBox>();
                var names = combos.Select(c => c.Name).ToList();
                var foreachNames = new List<string>();

                foreach (var comboBox in combos)
                {
                    foreachNames.Add(comboBox.Name);
                }

                Debug.WriteLine(String.Join(", ", names));
                Debug.WriteLine(String.Join(", ", foreachNames));
            }
        }

        private IEnumerable<Control> GetAll(Control control, Type type)
        {
            IEnumerable<Control> controls = control.Controls.Cast<Control>();

            return controls.SelectMany(ctrl => GetAll(ctrl, type))
                .Concat(controls)
                .Where(c => c.GetType() == type);
        }
    }
}

---

你能提供一个简短但完整的程序来演示这个问题吗？这对我来说很奇怪。我无法在我的末端重现这个问题。已尝试更改选项卡索引、Z顺序、可见和启用的属性。两种方法的顺序相同。你能解释一下完整的场景吗？很怀疑是否有人能从这个代码片段中得到复制，或者它是否与真实的代码匹配。Google Linq推迟执行以了解更多信息。问题似乎是由Infragistics UltraGroupBox引起的。我将添加适当的标记并发布独立代码。发布独立代码。这肯定是由UltraGroupBox引起的。也许我可以从基础设施人群那里得到一些澄清。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Diagnostics;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Windows.Forms;


namespace WindowsFormsApplication2
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            if (!DesignMode)
            {
                var combos = GetAll(this, typeof(ComboBox)).Cast<ComboBox>();
                var names = combos.Select(c => c.Name).ToList();
                var foreachNames = new List<string>();

                foreach (var comboBox in combos)
                {
                    foreachNames.Add(comboBox.Name);
                }

                Debug.WriteLine(String.Join(", ", names));
                Debug.WriteLine(String.Join(", ", foreachNames));
            }
        }

        private IEnumerable<Control> GetAll(Control control, Type type)
        {
            IEnumerable<Control> controls = control.Controls.Cast<Control>();

            return controls.SelectMany(ctrl => GetAll(ctrl, type))
                .Concat(controls)
                .Where(c => c.GetType() == type);
        }
    }
}