我有多个下拉列表框，所有查询相同的列，同一个表和来自同一个数据库。例如，在memberID列下，我有以下ID。
我有3个不同的下拉列表框，如下所示
<asp:DropDownList ID="memberID3" runat="server" Visible="false" OnSelectedIndexChanged="ddlpid3_SelectedIndexChanged" >
</asp:DropDownList>
<asp:DropDownList ID="memberID1" runat="server" Visible="false" OnSelectedIndexChanged="ddlpid1_SelectedIndexChanged">
</asp:DropDownList>
<asp:DropDownList ID="memberID2" runat="server" Visible="false" OnSelectedIndexChanged="ddlpid2_SelectedIndexChanged">
</asp:DropDownList>
我在下拉列表中添加了更新面板，以便我的下拉列表可以在任何更新/选择时刷新。
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
</ContentTemplate>
</asp:UpdatePanel>
例如，当memberID1选择12345时，另外2个下拉列表（memberID2和3）将不显示ID 12345.反之亦然，当memberID1选择下拉列表的默认值时，ID会再次出现在另外2个下拉列表框中。我为所有DDL添加了默认值。
memeberID(number).Items.Insert(0, new ListItem(" Please select a Member ID", ""));
memeberID(number).SelectedIndex = 0;
如果我没有弄错更新面板的属性，是不是能够使这个功能工作？
这是请求的绑定代码。
protected void ddllocation_SelectedIndexChanged(object sender, EventArgs e)
{
using (var connAdd = new SqlConnection("Data Source = localhost; Initial Catalog = MajorProject; Integrated Security= SSPI"))
{
connAdd.Open();
var sql = "Select policeid from PoliceAccount where status ='available' and handle ='offcase' and postedto='" + ddllocation.SelectedValue + "'";
using (var cmdAdd = new SqlDataAdapter(sql, connAdd))
{
DataSet ds2 = new DataSet();
cmdAdd.Fill(ds2);
memberID1.Items.Clear();
memberID1.DataSource = ds2;
memberID1.DataTextField = "memberID";
memberID1.DataValueField = "memberID";
memberID1.DataBind();
memberID1.Items.Insert(0, new ListItem("Please select a Member ID", ""));
memberID1.SelectedIndex = 0;
memberID2.Items.Clear();
memberID2.DataSource = ds2;
memberID2.DataTextField = "memberID";
memberID2.DataValueField = "memberID";
memberID2.DataBind();
memberID2.Items.Insert(0, new ListItem("Please select a Member ID", ""));
memberID2.SelectedIndex = 0;
memberID3.Items.Clear();
memberID3.DataSource = ds2;
memberID3.DataTextField = "memberID";
memberID3.DataValueField = "memberID";
memberID3.DataBind();
memberID3.Items.Insert(0, new ListItem("Please select a Member ID", ""));
memberID3.SelectedIndex = 0;
}
更新
现在，当选择默认值时，我可以允许我的其他ddl重新绑定并将所选值缓存在另一个下拉列表中。但是，当我选择其他ID时，ID将被删除，并且它不会重新绑定其他ddl。
protected void FillddlLocations()
{
FillDropdown(ddlpid1);
FillDropdown(ddlpid2);
FillDropdown(ddlpid3);
FillDropdown(ddlpid4);
FillDropdown(ddlpid5);
ddlpid1.Visible = false;
ddlpid2.Visible = false;
ddlpid3.Visible = false;
ddlpid4.Visible = false;
ddlpid5.Visible = false;
}
protected void FillDropdown(DropDownList ddl)
{
using (var connAdd = new SqlConnection("Data Source = localhost; Initial Catalog = MajorProject; Integrated Security= SSPI"))
{
connAdd.Open();
var sql = "Select policeid from PoliceAccount where status ='available' and handle ='offcase' and postedto='" + ddllocation.SelectedValue + "'";
using (var cmdAdd = new SqlDataAdapter(sql, connAdd))
{
DataSet ds2 = new DataSet();
cmdAdd.Fill(ds2);
ddl.Items.Clear();
ddl.DataSource = ds2;
ddl.DataBind();
ddl.Items.Insert(0, new ListItem("Police ID", ""));
ddl.SelectedIndex = 0;
}
}
}
protected void ddlpid1_SelectedIndexChanged(object sender, EventArgs e)
{
if (ddlpid1.SelectedIndex > 0)
{
Session["pid1"] = ddlpid1.SelectedValue;
ListItem removeItem2 = ddlpid2.Items.FindByValue(ddlpid1.SelectedValue);
ddlpid2.Items.Remove(removeItem2);
ListItem removeItem3 = ddlpid3.Items.FindByValue(ddlpid1.SelectedValue);
ddlpid3.Items.Remove(removeItem3);
ListItem removeItem4 = ddlpid4.Items.FindByValue(ddlpid1.SelectedValue);
ddlpid4.Items.Remove(removeItem4);
ListItem removeItem5 = ddlpid5.Items.FindByValue(ddlpid1.SelectedValue);
ddlpid5.Items.Remove(removeItem5);
}
else
if (ddlpid1.SelectedItem.Text.Equals("Police ID"))
{
FillDropdown(ddlpid1);
FillDropdown(ddlpid2);
FillDropdown(ddlpid3);
FillDropdown(ddlpid4);
FillDropdown(ddlpid5);
ddlpid2.SelectedValue = (String)Session["pid2"];
ddlpid2_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid3.SelectedValue = (String)Session["pid3"];
ddlpid3_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid4.SelectedValue = (String)Session["pid4"];
ddlpid4_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid5.SelectedValue = (String)Session["pid5"];
ddlpid5_SelectedIndexChanged(this, EventArgs.Empty);
}
}
protected void ddlpid2_SelectedIndexChanged(object sender, EventArgs e)
{
if (ddlpid2.SelectedIndex > 0)
{
Session["pid2"] = ddlpid2.SelectedValue;
ListItem removeItem1 = ddlpid1.Items.FindByValue(ddlpid2.SelectedValue);
ddlpid1.Items.Remove(removeItem1);
ListItem removeItem3 = ddlpid3.Items.FindByValue(ddlpid2.SelectedValue);
ddlpid3.Items.Remove(removeItem3);
ListItem removeItem4 = ddlpid4.Items.FindByValue(ddlpid2.SelectedValue);
ddlpid4.Items.Remove(removeItem4);
ListItem removeItem5 = ddlpid5.Items.FindByValue(ddlpid2.SelectedValue);
ddlpid5.Items.Remove(removeItem5);
}
else if (ddlpid2.SelectedItem.Text.Equals("Police ID"))
{
FillDropdown(ddlpid1);
FillDropdown(ddlpid2);
FillDropdown(ddlpid3);
FillDropdown(ddlpid4);
FillDropdown(ddlpid5);
ddlpid1.SelectedValue = (String)Session["pid1"];
ddlpid1_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid3.SelectedValue = (String)Session["pid3"];
ddlpid3_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid4.SelectedValue = (String)Session["pid4"];
ddlpid4_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid5.SelectedValue = (String)Session["pid5"];
ddlpid5_SelectedIndexChanged(this, EventArgs.Empty);
}
}
protected void ddlpid3_SelectedIndexChanged(object sender, EventArgs e)
{
if (ddlpid3.SelectedIndex > 0)
{
Session["pid3"] = ddlpid3.SelectedValue;
ListItem removeItem1 = ddlpid1.Items.FindByValue(ddlpid3.SelectedValue);
ddlpid1.Items.Remove(removeItem1);
ListItem removeItem2 = ddlpid2.Items.FindByValue(ddlpid3.SelectedValue);
ddlpid2.Items.Remove(removeItem2);
ListItem removeItem4 = ddlpid4.Items.FindByValue(ddlpid3.SelectedValue);
ddlpid4.Items.Remove(removeItem4);
ListItem removeItem5 = ddlpid5.Items.FindByValue(ddlpid3.SelectedValue);
ddlpid5.Items.Remove(removeItem5);
}
else if (ddlpid3.SelectedItem.Text.Equals("Police ID"))
{
FillDropdown(ddlpid1);
FillDropdown(ddlpid2);
FillDropdown(ddlpid3);
FillDropdown(ddlpid4);
FillDropdown(ddlpid5);
ddlpid1.SelectedValue = (String)Session["pid1"];
ddlpid1_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid2.SelectedValue = (String)Session["pid2"];
ddlpid2_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid4.SelectedValue = (String)Session["pid4"];
ddlpid4_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid5.SelectedValue = (String)Session["pid5"];
ddlpid5_SelectedIndexChanged(this, EventArgs.Empty);
}
}
protected void ddlpid4_SelectedIndexChanged(object sender, EventArgs e)
{
if (ddlpid4.SelectedIndex > 0)
{
Session["pid4"] = ddlpid4.SelectedValue;
ListItem removeItem1 = ddlpid1.Items.FindByValue(ddlpid4.SelectedValue);
ddlpid1.Items.Remove(removeItem1);
ListItem removeItem2 = ddlpid2.Items.FindByValue(ddlpid4.SelectedValue);
ddlpid2.Items.Remove(removeItem2);
ListItem removeItem3 = ddlpid3.Items.FindByValue(ddlpid4.SelectedValue);
ddlpid3.Items.Remove(removeItem3);
ListItem removeItem5 = ddlpid5.Items.FindByValue(ddlpid4.SelectedValue);
ddlpid5.Items.Remove(removeItem5);
}
else if (ddlpid4.SelectedItem.Text.Equals("Police ID"))
{
FillDropdown(ddlpid1);
FillDropdown(ddlpid2);
FillDropdown(ddlpid3);
FillDropdown(ddlpid4);
FillDropdown(ddlpid5);
ddlpid1.SelectedValue = (String)Session["pid1"];
ddlpid1_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid2.SelectedValue = (String)Session["pid2"];
ddlpid2_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid3.SelectedValue = (String)Session["pid3"];
ddlpid3_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid5.SelectedValue = (String)Session["pid5"];
ddlpid5_SelectedIndexChanged(this, EventArgs.Empty);
}
}
protected void ddlpid5_SelectedIndexChanged(object sender, EventArgs e)
{
if (ddlpid5.SelectedIndex > 0)
{
Session["pid5"] = ddlpid5.SelectedValue;
ListItem removeItem1 = ddlpid1.Items.FindByValue(ddlpid5.SelectedValue);
ddlpid1.Items.Remove(removeItem1);
ListItem removeItem2 = ddlpid2.Items.FindByValue(ddlpid5.SelectedValue);
ddlpid2.Items.Remove(removeItem2);
ListItem removeItem3 = ddlpid3.Items.FindByValue(ddlpid5.SelectedValue);
ddlpid3.Items.Remove(removeItem3);
ListItem removeItem4 = ddlpid4.Items.FindByValue(ddlpid5.SelectedValue);
ddlpid4.Items.Remove(removeItem4);
}
else if (ddlpid5.SelectedItem.Text.Equals("Police ID"))
{
FillDropdown(ddlpid1);
FillDropdown(ddlpid2);
FillDropdown(ddlpid3);
FillDropdown(ddlpid4);
FillDropdown(ddlpid5);
ddlpid1.SelectedValue = (String)Session["pid1"];
ddlpid1_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid2.SelectedValue = (String)Session["pid2"];
ddlpid2_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid3.SelectedValue = (String)Session["pid3"];
ddlpid3_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid4.SelectedValue = (String)Session["pid4"];
ddlpid4_SelectedIndexChanged(this, EventArgs.Empty);
}
}
答案 0 :(得分：1)
首先，我会在标记中将下拉列表的 AutoPostBack 属性设置为true：
<asp:DropDownList ID="memberID1" AutoPostBack="true" runat="server" Visible="false" OnSelectedIndexChanged="ddlpid1_SelectedIndexChanged">
</asp:DropDownList>
<asp:DropDownList ID="memberID2" AutoPostBack="true" runat="server" Visible="false" OnSelectedIndexChanged="ddlpid2_SelectedIndexChanged">
</asp:DropDownList>
<asp:DropDownList ID="memberID3" AutoPostBack="true" runat="server" Visible="false" OnSelectedIndexChanged="ddlpid3_SelectedIndexChanged" >
</asp:DropDownList>
更新：我们可以在视图状态中存储选定的值，并在重新填充下拉列表后检索：
public partial class WebForm2 : System.Web.UI.Page
{
bool bFlag = true;
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
FillddlLocations();
}
}
//Properties to store selected value in ViewState
protected string MemberID1Selection
{
get
{
if (ViewState["MemberID1Selection"] != null)
return ViewState["MemberID1Selection"].ToString();
return "";
}
set { ViewState["MemberID1Selection"] = value; }
}
protected string MemberID2Selection
{
get
{
if (ViewState["MemberID2Selection"] != null)
return ViewState["MemberID2Selection"].ToString();
return "";
}
set { ViewState["MemberID2Selection"] = value; }
}
protected string MemberID3Selection
{
get
{
if (ViewState["MemberID3Selection"] != null)
return ViewState["MemberID3Selection"].ToString();
return "";
}
set { ViewState["MemberID3Selection"] = value; }
}
protected void FillddlLocations()
{
FillDropdown(memberID1);
FillDropdown(memberID2);
FillDropdown(memberID3);
memberID1.Visible = true;
memberID2.Visible = true;
memberID3.Visible = true;
}
protected void FillDropdown(DropDownList ddl)
{
using (var connAdd = new SqlConnection("Data Source = localhost; Initial Catalog = MajorProject; Integrated Security= SSPI"))
{
connAdd.Open();
var sql = "Select policeid from PoliceAccount where status ='available' and handle ='offcase' and postedto='" + ddllocation.SelectedValue + "'";
using (var cmdAdd = new SqlDataAdapter(sql, connAdd))
{
DataSet ds2 = new DataSet();
cmdAdd.Fill(ds2);
ddl.Items.Clear();
ddl.DataSource = ds2;
ddl.DataTextField = "memberID";
ddl.DataValueField = "memberID";
ddl.DataBind();
ddl.Items.Insert(0, new ListItem("Please select a Member ID", ""));
ddl.SelectedIndex = 0;
}
}
}
protected void IndexChanged(DropDownList ddlChanged, DropDownList ddlToFilter1, DropDownList ddlToFilter2)
{
string removeValue1 = ddlChanged == memberID1 ? MemberID1Selection : (ddlChanged == memberID2 ? MemberID2Selection : MemberID3Selection);
string selValue2 = ddlChanged == memberID1 ? MemberID2Selection : (ddlChanged == memberID2 ? MemberID1Selection : MemberID1Selection);
string selValue3 = ddlChanged == memberID1 ? MemberID3Selection : (ddlChanged == memberID2 ? MemberID3Selection : MemberID2Selection);
bFlag = false;//Prevent fireing the code again while changing the index
if (removeValue1 != "")
{
ListItem item1 = ddlToFilter1.Items.FindByValue(removeValue1);
ddlToFilter1.Items.Remove(item1);
ListItem item2 = ddlToFilter2.Items.FindByValue(removeValue1);
ddlToFilter2.Items.Remove(item2);
}
if (selValue3 != "")
{
ListItem item3 = ddlToFilter1.Items.FindByValue(selValue3);
ddlToFilter1.Items.Remove(item3);
}
if (selValue2 != "")
{
ListItem item4 = ddlToFilter2.Items.FindByValue(selValue2);
ddlToFilter2.Items.Remove(item4);
}
bFlag = false;
ddlToFilter1.SelectedIndex = ddlToFilter1.Items.IndexOf(ddlToFilter1.Items.FindByValue(selValue2));
ddlToFilter2.SelectedIndex = ddlToFilter2.Items.IndexOf(ddlToFilter2.Items.FindByValue(selValue3));
}
protected void ddlpid1_SelectedIndexChanged(object sender, EventArgs e)
{
MemberID1Selection = memberID1.SelectedValue;
if (bFlag)
{
FillDropdown(memberID2);
FillDropdown(memberID3);
IndexChanged(memberID1, memberID2, memberID3);
}
}
protected void ddlpid2_SelectedIndexChanged(object sender, EventArgs e)
{
MemberID2Selection = memberID2.SelectedValue;
if (bFlag)
{
FillDropdown(memberID1);
FillDropdown(memberID3);
IndexChanged(memberID2, memberID1, memberID3);
}
}
protected void ddlpid3_SelectedIndexChanged(object sender, EventArgs e)
{
MemberID3Selection = memberID3.SelectedValue;
if (bFlag)
{
FillDropdown(memberID1);
FillDropdown(memberID2);
IndexChanged(memberID3, memberID1, memberID2);
}
}
}
我已经测试了代码，它对我有用。希望它有所帮助！