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我们刚刚将 ASP.NET Web 应用程序中的目标框架从 3.5 切换到 4.0。我们遇到了以下问题：

我们有几个自定义控件在 3.5 中运行良好，但现在在 4.0 中它们不会保留在 ViewState 中，其中一个基本上是继承 Label 类的其他控件的包装器，aspx 代码如下所示：

<fsc:FormLabel ID="l_purchaserNo" runat="server" CssClass="label" Text="Purchaser">
    <asp:TextBox ID="tb_purchaserNo" runat="server" CssClass="textBox" MaxLength="50" />
</fsc:FormLabel>

结果的html是：

<span id="l_purchaserNo" class="label">
    <label class="header" for="tb_purchaserNo">Purchaser</label>
    <span class="valueContainer">
        <input name="tb_purchaserNo" type="text" id="tb_purchaserNo" class="textBox" />
    </span>
</span>

所以控件基本上只是添加了一些跨度标签和一个连接到文本框的标签。

回发后 4.0 中的 html 代码是：

<span id="l_purchaserNo" class="label"></span>

即外包装中的所有内容都消失了，并且无法从后面的代码中检索到文本框中输入的任何内容。

您可以在下面找到我们的 FormLabel 类的代码。

我们发现，通过在我们的自定义控件 fsc:FormLabel 上设置 ViewStateMode=Disabled 和在 asp:TextBox 上设置 ViewStateMode=Enabled ，内部控件持续到 ViewState 但同时我们在包装器上丢失了 ViewState ，因为我们在包装器标签我们也需要视图状态（实际上我们尝试了每种组合并且在 fsc:FormLabel 上设置 ViewStateMode=Enabled 并没有帮助，无论我们如何在页面上设置 ViewStateMode）。EnableViewState 在所有级别上都是 true。

有人能告诉我们如何让 ViewState 在 3.5 中像以前一样在所有控件上工作 - 包装器和包装控件？

谢谢

克里斯蒂安、泽利科、乔纳斯

using System;
using System.Collections.Generic;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace FormLabel
{
    public class FormLabel : Label
    {
        private bool HasChildren
        {
            get
            {
                return Controls.Count > 0;
            }
        }

        public override string Text
        {
            get
            {
                if (!HasChildren)
                {
                    return base.Text;
                }

                var text = ViewState[ID + "Text"] as String;

                if (text != null)
                {
                    ((LiteralControl)Controls[0]).Text = text;
                }

                return ((LiteralControl)Controls[0]).Text;
            }
            set
            {
                if (!HasChildren)
                {
                    base.Text = value;
                    return;
                }

                ((LiteralControl)Controls[0]).Text = value;
            }
        }

        public void SetText(string text)
        {
            ((LiteralControl)Controls[0]).Text = text;
            ViewState[ID + "Text"] = text;
        }


        public bool IndicateRequired
        {
            get
            {
                object state = ViewState[String.Format("{0}_IR", ID)];
                return state != null && (bool)state;
            }
            set
            {
                ViewState[String.Format("{0}_IR", ID)] = value;
            }
        }

        protected override void OnLoad(EventArgs e)
        {           
            ViewState[ID + "Text"] = Text;
            base.OnLoad(e);
        }

        protected override void Render(HtmlTextWriter writer)
        {
            if (HasChildren)
            {
                List<Control> controls = Controls.GetControls();
                List<BaseValidator> validators = Controls.GetValidators();

                WriteLabelControl(writer);
                WriteRequiredIndicator(writer);
                WriteControlHeader(writer, validators, this.GetFirstControl());
                WriteInnerControls(writer, controls);
                WriteLabelEndControl(writer);

                return;
            }

            base.Render(writer);
        }

        private void WriteLabelControl(HtmlTextWriter writer)
        {
            writer.WriteBeginTag("span");
            writer.WriteAttribute("id", ClientID);
            writer.WriteAttribute("class", CssClass);

            foreach (string attributeKey in Attributes.Keys)
            {
                writer.WriteAttribute(attributeKey, Attributes[attributeKey]);
            }

            writer.Write(HtmlTextWriter.TagRightChar);
        }

        private void WriteRequiredIndicator(HtmlTextWriter writer)
        {
            if (IndicateRequired)
            {
                writer.WriteBeginTag("span");
                writer.WriteAttribute("class", "requiredIndicator");
                writer.Write(HtmlTextWriter.TagRightChar);
                writer.WriteEndTag("span");
            }
        }

        private void WriteControlHeader(HtmlTextWriter writer, IEnumerable<BaseValidator> validators, Control userControl)
        {
            writer.WriteBeginTag("label");
            writer.WriteAttribute("class", "header");

            if (userControl != null)
            {
                writer.WriteAttribute("for", userControl.ClientID);
            }

            writer.Write(HtmlTextWriter.TagRightChar);
            writer.Write(Text);

            foreach (BaseValidator validator in validators)
            {
                validator.CssClass = "Error";
                validator.RenderControl(writer);
            }

            writer.WriteEndTag("label");
        }

        private static void WriteInnerControls(HtmlTextWriter writer, IList<Control> controls)
        {
            writer.WriteBeginTag("span");
            writer.WriteAttribute("class", "valueContainer");
            writer.Write(HtmlTextWriter.TagRightChar);

            for (int i = 1; i < controls.Count; i++)
            {
                controls[i].RenderControl(writer);
            }

            writer.WriteEndTag("span");
        }

        private static void WriteLabelEndControl(HtmlTextWriter writer)
        {
            writer.WriteEndTag("span");
        }

    }

    #region Nested type: Extensions

    public static class Extensions
    {
        public static List<BaseValidator> GetValidators(this ControlCollection controls)
        {
            var validators = new List<BaseValidator>();

            foreach (Control c in controls)
            {
                if (c is BaseValidator)
                {
                    validators.Add(c as BaseValidator);
                }

            }

            return validators;
        }

        public static List<Control> GetControls(this ControlCollection controls)
        {
            var listcontrols = new List<Control>();

            foreach (Control c in controls)
            {
                if (!(c is BaseValidator))
                {
                    listcontrols.Add(c as Control);
                }

            }

            return listcontrols;
        }

        public static Control GetFirstControl(this Control container)
        {
            return (new InputControlFinder().FindFirstInputControl(container));
        }

        private class InputControlFinder
        {
            public Control FindFirstInputControl(Control control)
            {
                Control input = null;

                foreach (Control child in control.Controls)
                {
                    if (child is TextBox || child is DropDownList || child is CheckBox)
                    {
                        input = child;
                    }
                    else
                    {
                        input = FindFirstInputControl(child);
                    }

                    if (input != null)
                    {
                        return input;
                    }
                }

                return input;
            }
        }
    }
    #endregion
}
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