为什么Drop down在发回邮件后会重置? [英] Why Drop down gets reset after post back?

问题描述

我的要求是从下拉列表中选择一个值，然后获取相应的三个字段，并且下拉列表中必须具有所选的值. 但是我的代码将获取相应的三个字段，并将下拉选择的值设置为第一个值. 请告诉我如何解决此问题.

My requirement is to select a value from a drop down and fetch the corresponding three fields and drop down must have the selected value in it. However my code it fetches the corresponding three fields and sets the drop down selected value to first value. Please tel me how to solve this issue.

下面是我在页面加载时的代码和相应的方法:

Below are my code at page load and corresponding methods:

公共局部类RegisterWebPartUserControl:UserControl { 字符串titleid;

public partial class RegisterWebPartUserControl : UserControl { string titleid;

protected void Page_Load(object sender, EventArgs e)
{
DataSet ds = new DataSet();
SPSite oSPSiteCollection = SPContext.Current.Site;
SPWeb oSPWeb = SPContext.Current.Web;
SPList oSPList = oSPWeb.Lists["Registered"];
string names = oSPWeb.CurrentUser.ToString();
TxtEmployeeName.Text = names.ToString();
SPList oSPListCalender = oSPWeb.Lists["Scheduled Courses"];
DataTable dataTable = oSPListCalender.Items.GetDataTable();
dataTable.TableName = "Table1";
ds.Tables.Add(dataTable);
ddlDrop.DataSource = ds.Tables["Table1"];
ddlDrop.DataTextField = "Title";
ddlDrop.DataValueField = "TitleID";
titleid = ddlDrop.SelectedValue;
ddlDrop.DataBind();
}
protected void ddlDrop_SelectedIndexChanged(object sender, EventArgs e)
{
FetchReadOnlyFields(titleid);
}
public void FetchReadOnlyFields(string titleID)
{
string oStartDate = null;
string oEndDate = null;
string oPrerequisite = null;
SPSite oSPSiteCollection = SPContext.Current.Site;
SPWeb oSPWeb = SPContext.Current.Web;
SPList oSPList = oSPWeb.Lists["Registered"];
SPListItemCollection oItemCollection = oSPList.Items;
SPListItem ospListItem = oItemCollection.Add();
SPList oSPList1 = oSPWeb.Lists["Scheduled Courses"];
SPListItemCollection oItemCollectionCourse = oSPList1.Items;
SPFieldCalculated titleIDCourse = (SPFieldCalculated)oItemCollectionCourse.Fields["TitleID"];
SPField fieldStartDate = oItemCollectionCourse.Fields["Start Date"];
SPField fieldEndDate = oItemCollectionCourse.Fields["End Date"];
foreach (SPListItem ospListItemCourse in oItemCollectionCourse)
{
string value = titleIDCourse.GetFieldValueAsText(ospListItemCourse["TitleID"]);
if (titleID == value)
{
oPrerequisite = ospListItemCourse["Prerequisite"].ToString();
TxtPrerequisite1.Text = SPHttpUtility.ConvertSimpleHtmlToText(oPrerequisite, oPrerequisite.Length);
oStartDate = ospListItemCourse["Start Date"].ToString();
TxtStartDate.Text = oStartDate;
oEndDate = ospListItemCourse["End Date"].ToString();
TxtEndDate.Text = oEndDate;
break;
}
}
}
}

希望寻求您的帮助. 谢谢

Hope to seek your help. Thank you

推荐答案

此代码

ddlDrop.DataBind();

应该仅被调用一次.在页面的第一次加载上. 试试

Should be called only once. On the first load of the page. Try

protected void Page_Load(object sender, EventArgs e)
{
if(!Page.IsPostBack){ // this is what has changed
DataSet ds = new DataSet();
SPSite oSPSiteCollection = SPContext.Current.Site;
SPWeb oSPWeb = SPContext.Current.Web;
SPList oSPList = oSPWeb.Lists["Registered"];
string names = oSPWeb.CurrentUser.ToString();
TxtEmployeeName.Text = names.ToString();
SPList oSPListCalender = oSPWeb.Lists["Scheduled Courses"];
DataTable dataTable = oSPListCalender.Items.GetDataTable();
dataTable.TableName = "Table1";
ds.Tables.Add(dataTable);
ddlDrop.DataSource = ds.Tables["Table1"];
ddlDrop.DataTextField = "Title";
ddlDrop.DataValueField = "TitleID";

ddlDrop.DataBind();
}

titleid = ddlDrop.SelectedValue;
}

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