Hello,
i have 2 dropdown lists:
1- ddlCity: that display all cities in the database
2-ddlBranch:display all branches per city.
So once i select a city, related branches should be selected.
and i have a method in C# source code that clear my form which contains the 2 dropdownlists. So once i click on the "Clear" button, the 2 dropdown list should be empty:
1-ddlcity display: "--Select--"
2-ddlBranch display: "----"
Now the problem is that When i click on the button "Clear" an error message occurs: "
'ddlBranch' has a SelectedValue which is invalid because it does not exist in the list of items.
Parameter name: value
Please I need your help and thank you in advance.
Asp. Net Code:
<asp:DropDownList ID="ddlCity" runat="server" Width="170px"
DataSourceID="tblCity" DataTextField="city" DataValueField="cityID" AutoPostBack="true" AppendDataBoundItems="true"
onselectedindexchanged="ddlCity_SelectedIndexChanged">
<asp:ListItem Text="--Select--" Value=""></asp:ListItem>
<asp:SqlDataSource ID="tblCity" runat="server" ConnectionString="<%$ ConnectionStrings:SmartBookingEngineConn %>" SelectCommand="SELECT [cityID],[city] FROM [tblCity]"></asp:SqlDataSource>
<asp:DropDownList ID="ddlBranch" runat="server" Width="170px" AutoPostBack="true"
onselectedindexchanged="ddlBranch_SelectedIndexChanged" >
<asp:ListItem Text="----" Value="" Selected="True"></asp:ListItem>
</asp:DropDownList>
<telerik:RadAjaxManagerProxy ID="rp" runat="server">
</telerik:RadAjaxManagerProxy>
C# code:
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
ddlCity.DataBind();
if (ddlCity.SelectedValue !="")
{
dtbranch = null;
string selectedIDCity = ddlCity.SelectedValue;
string mysqlSelectBranch = "select Branch,CityID,BranchID from viewBranchPerCity where CityID=" + selectedIDCity;
dtbranch = db.sqlServer.SelectRecord(mysqlSelectBranch);
ddlBranch.DataSource = dtbranch;
ddlBranch.DataValueField = "BranchID";
ddlBranch.DataTextField = "Branch";
}
ddlBranch.DataBind();
}
rp.AjaxSettings.AddAjaxSetting(ddlCity, ddlBranch, RadAjaxLoadingPanel1);
}
protected void btnClear_Click(object sender, EventArgs e)
{
clearForm();
}
protected void clearForm()
{
ddlCity.Enabled = true;
ddlBranch.Enabled = true;
ddlCity.SelectedValue = string.Empty;
ddlBranch.SelectedValue = string.Empty;
}
protected void ddlCity_SelectedIndexChanged(object sender, EventArgs e)
{
dtbranch = null;
string selectedIDCity = ddlCity.SelectedValue;
string mysqlSelectBranch = "select Branch,CityID,BranchID from viewBranchPerCity where CityID=" + selectedIDCity;
dtbranch = db.sqlServer.SelectRecord(mysqlSelectBranch);
ddlBranch.DataSource = dtbranch;
ddlBranch.DataValueField = "BranchID";
ddlBranch.DataTextField = "Branch";
ddlBranch.DataBind();
}