我创建了一个表单，我根据PDF中的表单字段添加下拉列表。
namesMapping变量是Dictionary，其中旧值为键，新值为值。要保存值，我想将当前选择添加到Dictionary。 但是eventlistener没有开火。
我在这里读过许多帖子，说使用IsPostBack变量来更新页面重新加载时的下拉列表。但在这种情况下它似乎不起作用。
感觉从下拉列表中获取所选值会更容易。但无论如何，如何保存下拉列表中的选定值，以便在点击按钮后获取它们？
以下是代码：
protected void Page_Load(object sender, EventArgs e)
{
ListItem[] listItems = new ListItem[4];
listItems[0] = new ListItem("First Name", "first-name");
listItems[1] = new ListItem("Last Name", "last-name");
listItems[2] = new ListItem("Email", "email");
listItems[3] = new ListItem("Company", "company");
int counter = 0;
foreach (PdfField field in fields)
{
if (field.GetType() == typeof(PdfTextField))
{
TableRow tr = new TableRow();
TableCell name = new TableCell
{
Text = field.Name
};
tr.Cells.Add(name);
TableCell options = new TableCell();
DropDownList dropdown = new DropDownList();
dropdown.ID = field.Name;
for (int i = 0; i < listItems.Length; i++)
{
dropdown.Items.Add(listItems[i]);
}
dropdown.SelectedIndexChanged += Dropdown_SelectedIndexChanged;
options.Controls.Add(dropdown);
tr.Cells.Add(options);
Table1.Rows.Add(tr);
//If page loads for the first time, set the mapping to the default selected values
if (!IsPostBack)
{
namesMapping.Add(field.Name, dropdown.SelectedValue);
}
}
}
private void Dropdown_SelectedIndexChanged(object sender, EventArgs e)
{
DropDownList dropDown = (DropDownList) sender;
namesMapping[dropDown.ID] = dropDown.SelectedValue;
}
感谢您的回答。
修改
我将创建下拉列表的代码移动到if(!IsPostBack)以内，以便在重新加载页面时不会重新创建它们。我将所有下拉列表保存在Dictionary中，但在下拉列表中选择另一个时，它们仍会显示第一个值。
以下是代码：
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
doc = new PdfDocument(pdfFileName);
namesMapping = new Dictionary<string, string>();
ddlMappings = new Dictionary<string, DropDownList>();
//Get all fields
fields = doc.Fields;
//Create the dropdown lists
dropdownLists = new List<DropDownList>();
ListItem[] listItems = new ListItem[4];
listItems[0] = new ListItem("First Name", "first-name");
listItems[1] = new ListItem("Last Name", "last-name");
listItems[2] = new ListItem("Email", "email");
listItems[3] = new ListItem("Company", "company");
int counter = 0;
foreach (PdfField field in fields)
{
//Only display the text fields
if (field.GetType() == typeof(PdfTextField))
{
TableRow tr = new TableRow();
//Add the field name
TableCell name = new TableCell
{
Text = field.Name
};
tr.Cells.Add(name);
//Add the options to select from
TableCell options = new TableCell();
DropDownList dropdown = new DropDownList();
dropdown.ID = field.Name;
//Populate the dropdown
for (int i = 0; i < listItems.Length; i++)
{
dropdown.Items.Add(listItems[i]);
}
dropdown.AutoPostBack = true;
dropdown.SelectedIndexChanged += Dropdown_SelectedIndexChanged;
options.Controls.Add(dropdown);
tr.Cells.Add(options);
//Add row to table
Table1.Rows.Add(tr);
//If page loads for the first time, set the mapping to the default selected values
namesMapping.Add(field.Name, dropdown.SelectedValue);
ddlMappings.Add(field.Name, dropdown);
}
}
}
else
{
foreach (PdfField field in fields)
{
//Only display the text fields
if (field.GetType() == typeof(PdfTextField))
{
TableRow tr = new TableRow();
//Add the field name
TableCell name = new TableCell
{
Text = field.Name
};
tr.Cells.Add(name);
//Add the options to select from
TableCell options = new TableCell();
DropDownList dropdown = ddlMappings[field.Name];
dropdown.SelectedIndexChanged += Dropdown_SelectedIndexChanged;
options.Controls.Add(dropdown);
tr.Cells.Add(options);
//Add row to table
Table1.Rows.Add(tr);
}
}
}
if (!IsPostBack)
{
foreach(var ddl in ddlMappings)
{
ddl.Value.SelectedValue = namesMapping[ddl.Key];
}
}
}
private void Dropdown_SelectedIndexChanged(object sender, EventArgs e)
{
DropDownList dropDown = (DropDownList) sender;
namesMapping[dropDown.ID] = dropDown.SelectedValue;
}
答案 0 :(得分：0)
如果你在Page_Load中进行数据绑定，那么你也会重置SelectedItem。
您应该在Page_Load块中添加if(!IsPostBack)中存在的绑定代码。
if(!Page.IsPostBack)
{
// Your binding code here ...
}
以下是您进行绑定的代码示例...
<form id="form1" runat="server">
<div>
<asp:DropDownList ID="DropDownList1" runat="server" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged" AutoPostBack="true"></asp:DropDownList>
</div>
</form>
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack) {
Bind();
}
}
protected void Bind() {
DataTable dt = new DataTable();
DataColumn dc = new DataColumn("Name", typeof(string));
DataColumn dc2 = new DataColumn("Path", typeof(string));
dt.Columns.Add(dc);
dt.Columns.Add(dc2);
DataRow dr = dt.NewRow();
dr["Name"] = "1";
dr["Path"] = Server.MapPath("ProDinner1.pdf");
DataRow dr2 = dt.NewRow();
dr2["Name"] = "2";
dr2["Path"] = Server.MapPath("ProDinner2.pdf");
dt.Rows.Add(dr);
dt.Rows.Add(dr2);
DropDownList1.DataSource = dt;
DropDownList1.DataTextField = "Name";
DropDownList1.DataValueField = "Path";
DropDownList1.DataBind();
}
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
string path = DropDownList1.SelectedValue.ToString();
Session["path"] = path;
Response.Write("<script language=javascript>window.open('show.aspx')</script>");
}
答案 1 :(得分：0)
阅读本文后，我找到了解决问题的方法：
Maintain The State Of Dynamic Added User Control On Each PostBack
我使用ViewState来保存下拉列表的ID，以便能够在Postback上重新创建它们。这是代码：
public Dictionary<Guid, string> DropdownLists
{
get { return ViewState["MyDropdowns"] != null
? (Dictionary<Guid, string>)ViewState["MyDropdowns"] : new Dictionary<Guid, string>(); }
set { ViewState["MyDropdowns"] = value; }
}
public Dictionary<Guid, string> DropdownNames
{
get { return ViewState["DropdownNames"] != null
? (Dictionary<Guid, string>)ViewState["DropdownNames"] : new Dictionary<Guid, string>(); }
set { ViewState["DropdownNames"] = value; }
}
首先，我添加了这两个类变量，将其值保存在ViewState中。然后第一次加载页面时调用方法CreateForm()，根据PDF文件中的字段创建所有下拉列表。在回发时加载页面时，将根据ViewState中存储的值创建下拉列表。代码如下：
protected void Page_Load()
{
//Load the file
doc = new PdfDocument(pdfFileName);
//Get all fields
fields = doc.Fields;
if (!IsPostBack)
{
CreateForm();
}
else
{
RecreateForm();
}
}
private void CreateForm()
{
Dictionary<Guid, string> tempList = new Dictionary<Guid, string>();
Dictionary<Guid, string> tempNames = new Dictionary<Guid, string>();
foreach (PdfField field in fields)
{
//Only display the text fields
if (field.GetType() == typeof(PdfTextField))
{
TableRow tr = new TableRow();
TableCell name = new TableCell
{
Text = field.Name
};
tr.Cells.Add(name);
TableCell options = new TableCell();
DropdownList dropdown = (DropdownList)LoadControl("~/DropdownList.ascx");
Guid nextKey = Guid.NewGuid();
tempList[nextKey] = "dropdown" + nextKey.ToString().Replace('-', '_');
dropdown.ID = tempList[nextKey];
tempNames[nextKey] = field.Name;
options.Controls.Add(dropdown);
tr.Cells.Add(options);
Table1.Rows.Add(tr);
}
}
DropdownLists = tempList;
DropdownNames = tempNames;
}
private void RecreateForm()
{
foreach (var item in DropdownLists)
{
TableRow tr = new TableRow();
TableCell name = new TableCell
{
Text = DropdownNames[item.Key]
};
tr.Cells.Add(name);
TableCell options = new TableCell();
DropdownList dropdown = (DropdownList)LoadControl("~/DropdownList.ascx");
dropdown.ID = DropdownLists[item.Key];
options.Controls.Add(dropdown);
tr.Cells.Add(options);
Table1.Rows.Add(tr);
}
}
我希望这可以帮助那里的任何人。