【发布时间】：2013-03-26 15:21:56
【问题描述】：
我已经阅读了很多关于 viewstate 的文章，但我无法理解它。
基本上我想要两个带有添加和删除按钮的列表框和一个继续按钮。
按下“继续”按钮时，前一个被隐藏，第一个列表框中的每个项目都会显示一个文本框，其中有 2 个下拉框来描述它+第二个列表框中的每个项目都有一个文本框（也适用于用户添加描述）。
然后我想要一个完成按钮来将所有这些信息保存到数据库中。
到目前为止，我有以下代码：
<script runat="server">
void Page_Load(Object sender, EventArgs e)
{
CreateDynamicControls();
Page.MaintainScrollPositionOnPostBack = true;
Build2.Visible = false;
Build3.Visible = false;
Build4.Visible = false;
Finish.Visible = false;
}
void AddC_Click(Object sender, EventArgs e)
{
criteria.Items.Add(addnewc.Text.ToString());
addnewc.Text = null;
}
void RemoveCriterion_Click(Object sender, EventArgs e)
{
for (int i = 0; i < criteria.Items.Count; i++)
{
if (criteria.Items[i].Selected)
{
criteria.Items.Remove(criteria.Items[i]);
i--;
}
}
}
void AddAlternative_Click(Object sender, EventArgs e)
{
alternatives.Items.Add(addnewa.Text.ToString());
addnewa.Text = null;
}
void RemoveAlternative_Click(Object sender, EventArgs e)
{
for (int i = 0; i < alternatives.Items.Count; i++)
{
if (alternatives.Items[i].Selected)
{
alternatives.Items.Remove(alternatives.Items[i]);
i--;
}
}
}
void Continue_Click(Object sender, EventArgs e)
{
Build1.Visible = false;
Build2.Visible = true;
Build3.Visible = true;
CreateDynamicControls();
Finish.Visible = true;
}
void CreateDynamicControls()
{
Build2.Controls.Clear();
Build3.Controls.Clear();
Build2.Controls.Add(new LiteralControl("<h3>Please define each criterion.</h3><p>By describing it and indicating if it is 1/2 and a/b.</p>"));
for (int i = 0; i < criteria.Items.Count; i++)
{
Build2.Controls.Add(new LiteralControl("<strong>" + criteria.Items[i].Text + "</strong> Description:<br />"));
TextBox criteriondesc = new TextBox();
Build2.Controls.Add(criteriondesc);
criteriondesc.ID = "c" + i.ToString();
criteriondesc.Rows = 3;
criteriondesc.Width = 850;
criteriondesc.TextMode = TextBoxMode.MultiLine;
Build2.Controls.Add(new LiteralControl("<br />"));
Build2.Controls.Add(new LiteralControl("Desc1: "));
DropDownList aim = new DropDownList();
aim.ID = i.ToString();
aim.Width = 250;
aim.Items.Add(new ListItem("1"));
aim.Items.Add(new ListItem("2"));
Build2.Controls.Add(aim);
Build2.Controls.Add(new LiteralControl(" Desc2: "));
DropDownList source = new DropDownList();
source.ID = i.ToString();
source.Width = 250;
source.Items.Add(new ListItem("a"));
source.Items.Add(new ListItem("b"));
Build2.Controls.Add(source);
Build2.Controls.Add(new LiteralControl("<br /><br />"));
}
Build3.Controls.Add(new LiteralControl("<h3>Please define each alternative.</h3><p>Please describe each alternaitve in detail.</p>"));
for (int i = 0; i < alternatives.Items.Count; i++)
{
Build3.Controls.Add(new LiteralControl("<strong>" + alternatives.Items[i].Text + "</strong> Description:<br />"));
TextBox altdesc = new TextBox();
altdesc.ID = "a" + i.ToString();
altdesc.Rows = 3;
altdesc.Width = 850;
altdesc.TextMode = TextBoxMode.MultiLine;
Build3.Controls.Add(altdesc);
Build3.Controls.Add(new LiteralControl("<br />"));
}
Build3.Controls.Add(new LiteralControl("<br /><h3>Review dates.</h3><p>Please select a date for a meeting.</p>"));
OboutInc.Calendar2.Calendar selectdates = new OboutInc.Calendar2.Calendar();
Build3.Controls.Add(selectdates);
}
void Finish_Click(Object sender, EventArgs e)
{
Build4.Visible = true;
foreach (var control in Build2.Controls)
{
if (control.GetType() == typeof(TextBox))
{
Build4.Controls.Add(new LiteralControl(((TextBox)control).Text + "<br>"));
}
}
foreach (var control in Build3.Controls)
{
if (control.GetType() == typeof(TextBox))
{
Build4.Controls.Add(new LiteralControl(((TextBox)control).Text + "<br>"));
}
}
}
</script>
<asp:Content runat="server" ID="MainContent" ContentPlaceHolderID="MainContent">
<asp:Panel ID="Build1" runat="server">
<h3>What is your aim?</h3>
<p>
<asp:TextBox ID="goal" runat="server" Width="850px"></asp:TextBox>
</p>
<h3>What are the criteria of your decision?</h3>
<p>
<asp:ListBox ID="criteria" runat="server" Rows="8" Width="850px"></asp:ListBox><br />
<asp:Button ID="RemoveCriterion" runat="server" Text="Remove" OnClick="RemoveCriterion_Click" />
<asp:TextBox ID="addnewc" runat="server" Width="650px"></asp:TextBox>
<asp:Button ID="AddC" runat="server" Text="Add" OnClick="AddC_Click" />
</p>
</p>
<h3>What are the alternatives of your decision?</h3>
<p>
<asp:ListBox ID="alternatives" runat="server" Rows="8" Width="850px"></asp:ListBox><br />
<asp:Button ID="RemoveAlternative" runat="server" Text="Remove" OnClick="RemoveAlternative_Click" />
<asp:TextBox ID="addnewa" runat="server" Width="650px"></asp:TextBox>
<asp:Button ID="AddAlternative" runat="server" Text="Add" OnClick="AddAlternative_Click" />
</p>
<p align="right"><asp:Button ID="continue" runat="server" Text="Continue" OnClick="Continue_Click" /></p>
</asp:Panel>
<asp:Panel ID="Build2" runat="server">
</asp:Panel>
<asp:Panel ID="Build3" runat="server">
</asp:Panel>
<asp:Panel ID="Build4" runat="server">
</asp:Panel>
<p align="right"><asp:Button ID="Finish" runat="server" Text="Finish" OnClick="Finish_Click" /></p>
</asp:Content>
如您所见，此刻我只是试图从动态创建的文本框字段中输出用户的文本。
但是，我得到了错误
加载视图状态失败。视图状态所在的控制树 正在加载的必须与用于保存的控制树匹配 上一个请求期间的视图状态。例如，当添加 动态控制，回发期间添加的控件必须匹配 在初始阶段添加的控件的类型和位置 请求。
在：第 169 行：Build3.Controls.Add(altdesc);
有谁知道如何用视图状态解决这个问题？
我是 ASP.NET 的新手，我的背景主要是 WinForms。
感谢您的任何帮助和建议！
【问题讨论】：
-
这对控制丢失有帮助吗？
-
是的，因为它会阻止您遇到此类问题。这些控件将自动（重新）创建动态控件。您可以使用模板字段，然后您就可以使用任何控件。
标签： asp.net dynamic controls viewstate