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asp.net webcontrols : How to Reference Gridview child controls
I have a gridview that I want to basically convert to behavior like Excel autofilter. I have created a dropdown list and put it into the header of the gridview, but I can't seem to reference it correctly. I have been trolling through the net and ms references for hours but I can't get it straight. Here is the html code: <%@ Page Language="VB" AutoEventWireup="false" CodeFile="datagridtest4.aspx.vb" Inherits="datagridtest4" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server"> <title>Untitled Page</title> </head> <body> <form id="form1" runat="server"> <div> </div> <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataSourceID="AccessDataSource1"> <Columns> <asp:TemplateField HeaderText="Vendor" SortExpression="Vendor"> <EditItemTemplate> <asp:TextBox ID="TextBox1" runat="server" Text='<%# Bind("Vendor") %>'></asp:TextBox> </EditItemTemplate> <HeaderTemplate> <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" DataSourceID="AccessDataSource1" DataTextField="Vendor" DataValueField="VendorID" onselectedindexchanged="DropDownList1_SelectedIndexChanged"> </asp:DropDownList> <asp:AccessDataSource ID="AccessDataSource1" runat="server" DataFile="~/App_Data/courses.mdb" SelectCommand="SELECT * FROM [tblVendors] ORDER BY [Vendor]"> </asp:AccessDataSource> </HeaderTemplate> <ItemTemplate> <asp:Label ID="Label1" runat="server" Text='<%# Bind("Vendor") %>'></asp:Label> </ItemTemplate> </asp:TemplateField> <asp:BoundField DataField="BasicCourseName" HeaderText="BasicCourseName" SortExpression="BasicCourseName" /> </Columns> </asp:GridView> <asp:AccessDataSource ID="AccessDataSource1" runat="server" DataFile="~/App_Data/courses.mdb" SelectCommand="SELECT * FROM [qryCoursesByVendors]"></asp:AccessDataSource> </form> </body> </html> I don't know where to attach the code behind the form; on the dropdown list changed event, or the page load event, or...? I am sorry if this is stupid, but I can't seem to get it. Here is what I have in the code behind the form: Protected Sub DropDownList1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Dim ddlVendor As DropDownList ddlVendor = Me.GridView1.FindControl("DropDownList1") AccessDataSource1.FilterExpression = "VendorID = " & ddlVendor.SelectedItem.Text End Sub I have also experimented with: ddlVendor = CType(GridView1.TemplateControl.FindControl("DropDownList1"), DropDownList) I get the following error message: Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.NullReferenceException: Object reference not set to an instance of an object. Source Error: Line 36: Dim ddlVendor As DropDownList Line 37: ddlVendor = Me.GridView1.FindControl("DropDownList1") Line 38: AccessDataSource1.FilterExpression = "VendorID = " & ddlVendor.SelectedItem.Text Line 39: End If Is there any way to implement this type of thing, or is this a nightmare? I am a beginning programmer, and I've already spent many days making only incremental advances. thanks in advance for your help and support. mike
Anyone? I'm still stuck! Thanks!
[quoted text, click to view] "Mike" wrote:
> Hello, > > I have a gridview that I want to basically convert to behavior like Excel > autofilter. I have created a dropdown list and put it into the header of the > gridview, but I can't seem to reference it correctly. I have been trolling > through the net and ms references for hours but I can't get it straight. > > Here is the html code: > > <%@ Page Language="VB" AutoEventWireup="false" > CodeFile="datagridtest4.aspx.vb" Inherits="datagridtest4" %> > > <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" > "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> > > <html xmlns="http://www.w3.org/1999/xhtml"> > <head runat="server"> > <title>Untitled Page</title> > </head> > <body> > <form id="form1" runat="server"> > <div> > > </div> > <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" > DataSourceID="AccessDataSource1"> > <Columns> > <asp:TemplateField HeaderText="Vendor" SortExpression="Vendor"> > <EditItemTemplate> > <asp:TextBox ID="TextBox1" runat="server" Text='<%# > Bind("Vendor") %>'></asp:TextBox> > </EditItemTemplate> > <HeaderTemplate> > <asp:DropDownList ID="DropDownList1" runat="server" > AutoPostBack="True" > DataSourceID="AccessDataSource1" > DataTextField="Vendor" > DataValueField="VendorID" > > onselectedindexchanged="DropDownList1_SelectedIndexChanged"> > </asp:DropDownList> > <asp:AccessDataSource ID="AccessDataSource1" > runat="server" > DataFile="~/App_Data/courses.mdb" > SelectCommand="SELECT * FROM [tblVendors] ORDER BY > [Vendor]"> > </asp:AccessDataSource> > </HeaderTemplate> > <ItemTemplate> > <asp:Label ID="Label1" runat="server" Text='<%# > Bind("Vendor") %>'></asp:Label> > </ItemTemplate> > </asp:TemplateField> > <asp:BoundField DataField="BasicCourseName" > HeaderText="BasicCourseName" > SortExpression="BasicCourseName" /> > </Columns> > </asp:GridView> > <asp:AccessDataSource ID="AccessDataSource1" runat="server" > DataFile="~/App_Data/courses.mdb" > SelectCommand="SELECT * FROM > [qryCoursesByVendors]"></asp:AccessDataSource> > </form> > </body> > </html> > > > I don't know where to attach the code behind the form; on the dropdown list > changed event, or the page load event, or...? I am sorry if this is stupid, > but I can't seem to get it. Here is what I have in the code behind the form: > > Protected Sub DropDownList1_SelectedIndexChanged(ByVal sender As Object, > ByVal e As System.EventArgs) > > Dim ddlVendor As DropDownList > ddlVendor = Me.GridView1.FindControl("DropDownList1") > AccessDataSource1.FilterExpression = "VendorID = " & > ddlVendor.SelectedItem.Text > > End Sub > > I have also experimented with: > ddlVendor = CType(GridView1.TemplateControl.FindControl("DropDownList1"), > DropDownList) > > I get the following error message: > > Description: An unhandled exception occurred during the execution of the > current web request. Please review the stack trace for more information about > the error and where it originated in the code. > > Exception Details: System.NullReferenceException: Object reference not set > to an instance of an object. > > Source Error: > > > Line 36: Dim ddlVendor As DropDownList > Line 37: ddlVendor = Me.GridView1.FindControl("DropDownList1") > Line 38: AccessDataSource1.FilterExpression = "VendorID = " & > ddlVendor.SelectedItem.Text > Line 39: End If > > > Is there any way to implement this type of thing, or is this a nightmare? I > am a beginning programmer, and I've already spent many days making only > incremental advances. > > thanks in advance for your help and support. > > mike >
A little more update, I've also tried:
Dim ddlVendorFilter As DropDownList = CType(gvCourses.FindControl("ddlVendor"), DropDownList) MsgBox("ddlVendor Selected Value is" & ddlVendorFilter.SelectedValue) 'Returns error [quoted text, click to view] "Mike" wrote:
> Hello, > > I have a gridview that I want to basically convert to behavior like Excel > autofilter. I have created a dropdown list and put it into the header of the > gridview, but I can't seem to reference it correctly. I have been trolling > through the net and ms references for hours but I can't get it straight. > > Here is the html code: > > <%@ Page Language="VB" AutoEventWireup="false" > CodeFile="datagridtest4.aspx.vb" Inherits="datagridtest4" %> > > <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" > "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> > > <html xmlns="http://www.w3.org/1999/xhtml"> > <head runat="server"> > <title>Untitled Page</title> > </head> > <body> > <form id="form1" runat="server"> > <div> > > </div> > <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" > DataSourceID="AccessDataSource1"> > <Columns> > <asp:TemplateField HeaderText="Vendor" SortExpression="Vendor"> > <EditItemTemplate> > <asp:TextBox ID="TextBox1" runat="server" Text='<%# > Bind("Vendor") %>'></asp:TextBox> > </EditItemTemplate> > <HeaderTemplate> > <asp:DropDownList ID="DropDownList1" runat="server" > AutoPostBack="True" > DataSourceID="AccessDataSource1" > DataTextField="Vendor" > DataValueField="VendorID" > > onselectedindexchanged="DropDownList1_SelectedIndexChanged"> > </asp:DropDownList> > <asp:AccessDataSource ID="AccessDataSource1" > runat="server" > DataFile="~/App_Data/courses.mdb" > SelectCommand="SELECT * FROM [tblVendors] ORDER BY > [Vendor]"> > </asp:AccessDataSource> > </HeaderTemplate> > <ItemTemplate> > <asp:Label ID="Label1" runat="server" Text='<%# > Bind("Vendor") %>'></asp:Label> > </ItemTemplate> > </asp:TemplateField> > <asp:BoundField DataField="BasicCourseName" > HeaderText="BasicCourseName" > SortExpression="BasicCourseName" /> > </Columns> > </asp:GridView> > <asp:AccessDataSource ID="AccessDataSource1" runat="server" > DataFile="~/App_Data/courses.mdb" > SelectCommand="SELECT * FROM > [qryCoursesByVendors]"></asp:AccessDataSource> > </form> > </body> > </html> > > > I don't know where to attach the code behind the form; on the dropdown list > changed event, or the page load event, or...? I am sorry if this is stupid, > but I can't seem to get it. Here is what I have in the code behind the form: > > Protected Sub DropDownList1_SelectedIndexChanged(ByVal sender As Object, > ByVal e As System.EventArgs) > > Dim ddlVendor As DropDownList > ddlVendor = Me.GridView1.FindControl("DropDownList1") > AccessDataSource1.FilterExpression = "VendorID = " & > ddlVendor.SelectedItem.Text > > End Sub > > I have also experimented with: > ddlVendor = CType(GridView1.TemplateControl.FindControl("DropDownList1"), > DropDownList) > > I get the following error message: > > Description: An unhandled exception occurred during the execution of the > current web request. Please review the stack trace for more information about > the error and where it originated in the code. > > Exception Details: System.NullReferenceException: Object reference not set > to an instance of an object. > > Source Error: > > > Line 36: Dim ddlVendor As DropDownList > Line 37: ddlVendor = Me.GridView1.FindControl("DropDownList1") > Line 38: AccessDataSource1.FilterExpression = "VendorID = " & > ddlVendor.SelectedItem.Text > Line 39: End If > > > Is there any way to implement this type of thing, or is this a nightmare? I > am a beginning programmer, and I've already spent many days making only > incremental advances. > > thanks in advance for your help and support. > > mike >
OK OK for what it's worth, here is the result of my stupid 25 hours of
digging...sheesh! This does not throw an error: Dim ddlVendorFilter As DropDownList = gvCourses.HeaderRow.FindControl("ddlVendor") I have not tried including it in a Ctype expression, and I'm not sure it's necessary... The key is including the HeaderRow in the code, because the control is in the headerRow...I guess this is "duh!" for many of you, but perhaps it may help a fool like me save several days of frustration...good luck! [quoted text, click to view] "Mike" wrote:
> A little more update, I've also tried: > > Dim ddlVendorFilter As DropDownList = > CType(gvCourses.FindControl("ddlVendor"), DropDownList) > > MsgBox("ddlVendor Selected Value is" & > ddlVendorFilter.SelectedValue) 'Returns error > > "Mike" wrote: > > > Hello, > > > > I have a gridview that I want to basically convert to behavior like Excel > > autofilter. I have created a dropdown list and put it into the header of the > > gridview, but I can't seem to reference it correctly. I have been trolling > > through the net and ms references for hours but I can't get it straight. > > > > Here is the html code: > > > > <%@ Page Language="VB" AutoEventWireup="false" > > CodeFile="datagridtest4.aspx.vb" Inherits="datagridtest4" %> > > > > <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" > > "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> > > > > <html xmlns="http://www.w3.org/1999/xhtml"> > > <head runat="server"> > > <title>Untitled Page</title> > > </head> > > <body> > > <form id="form1" runat="server"> > > <div> > > > > </div> > > <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" > > DataSourceID="AccessDataSource1"> > > <Columns> > > <asp:TemplateField HeaderText="Vendor" SortExpression="Vendor"> > > <EditItemTemplate> > > <asp:TextBox ID="TextBox1" runat="server" Text='<%# > > Bind("Vendor") %>'></asp:TextBox> > > </EditItemTemplate> > > <HeaderTemplate> > > <asp:DropDownList ID="DropDownList1" runat="server" > > AutoPostBack="True" > > DataSourceID="AccessDataSource1" > > DataTextField="Vendor" > > DataValueField="VendorID" > > > > onselectedindexchanged="DropDownList1_SelectedIndexChanged"> > > </asp:DropDownList> > > <asp:AccessDataSource ID="AccessDataSource1" > > runat="server" > > DataFile="~/App_Data/courses.mdb" > > SelectCommand="SELECT * FROM [tblVendors] ORDER BY > > [Vendor]"> > > </asp:AccessDataSource> > > </HeaderTemplate> > > <ItemTemplate> > > <asp:Label ID="Label1" runat="server" Text='<%# > > Bind("Vendor") %>'></asp:Label> > > </ItemTemplate> > > </asp:TemplateField> > > <asp:BoundField DataField="BasicCourseName" > > HeaderText="BasicCourseName" > > SortExpression="BasicCourseName" /> > > </Columns> > > </asp:GridView> > > <asp:AccessDataSource ID="AccessDataSource1" runat="server" > > DataFile="~/App_Data/courses.mdb" > > SelectCommand="SELECT * FROM > > [qryCoursesByVendors]"></asp:AccessDataSource> > > </form> > > </body> > > </html> > > > > > > I don't know where to attach the code behind the form; on the dropdown list > > changed event, or the page load event, or...? I am sorry if this is stupid, > > but I can't seem to get it. Here is what I have in the code behind the form: > > > > Protected Sub DropDownList1_SelectedIndexChanged(ByVal sender As Object, > > ByVal e As System.EventArgs) > > > > Dim ddlVendor As DropDownList > > ddlVendor = Me.GridView1.FindControl("DropDownList1") > > AccessDataSource1.FilterExpression = "VendorID = " & > > ddlVendor.SelectedItem.Text > > > > End Sub > > > > I have also experimented with: > > ddlVendor = CType(GridView1.TemplateControl.FindControl("DropDownList1"), > > DropDownList) > > > > I get the following error message: > > > > Description: An unhandled exception occurred during the execution of the > > current web request. Please review the stack trace for more information about > > the error and where it originated in the code. > > > > Exception Details: System.NullReferenceException: Object reference not set > > to an instance of an object. > > > > Source Error: > > > > > > Line 36: Dim ddlVendor As DropDownList > > Line 37: ddlVendor = Me.GridView1.FindControl("DropDownList1") > > Line 38: AccessDataSource1.FilterExpression = "VendorID = " & > > ddlVendor.SelectedItem.Text > > Line 39: End If > > > > > > Is there any way to implement this type of thing, or is this a nightmare? I > > am a beginning programmer, and I've already spent many days making only > > incremental advances. > > > > thanks in advance for your help and support. > > > > mike > >
[quoted text, click to view]
On Feb 21, 3:46 am, Mike <M...@discussions.microsoft.com> wrote: > OK OK for what it's worth, here is the result of my stupid 25 hours of > digging...sheesh! > > This does not throw an error: > > Dim ddlVendorFilter As DropDownList = > gvCourses.HeaderRow.FindControl("ddlVendor") > > I have not tried including it in a Ctype expression, and I'm not sure it's > necessary... > > The key is including the HeaderRow in the code, because the control is in > the headerRow...I guess this is "duh!" for many of you, but perhaps it may > help a fool like me save several days of frustration...good luck! > > "Mike" wrote: > > A little more update, I've also tried: > > > Dim ddlVendorFilter As DropDownList = > > CType(gvCourses.FindControl("ddlVendor"), DropDownList) > > > MsgBox("ddlVendor Selected Value is" & > > ddlVendorFilter.SelectedValue) 'Returns error > > > "Mike" wrote: > > > > Hello, > > > > I have a gridview that I want to basically convert to behavior like Excel > > > autofilter. I have created a dropdown list and put it into the header of the > > > gridview, but I can't seem to reference it correctly. I have been trolling > > > through the net and ms references for hours but I can't get it straight. > > > > Here is the html code: > > > > <%@ Page Language="VB" AutoEventWireup="false" > > > CodeFile="datagridtest4.aspx.vb" Inherits="datagridtest4" %> > > > > <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" > > > "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> > > > > <html xmlns="http://www.w3.org/1999/xhtml"> > > > <head runat="server"> > > > <title>Untitled Page</title> > > > </head> > > > <body> > > > <form id="form1" runat="server"> > > > <div> > > > > </div> > > > <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" > > > DataSourceID="AccessDataSource1"> > > > <Columns> > > > <asp:TemplateField HeaderText="Vendor" SortExpression="Vendor"> > > > <EditItemTemplate> > > > <asp:TextBox ID="TextBox1" runat="server" Text='<%# > > > Bind("Vendor") %>'></asp:TextBox> > > > </EditItemTemplate> > > > <HeaderTemplate> > > > <asp:DropDownList ID="DropDownList1" runat="server" > > > AutoPostBack="True" > > > DataSourceID="AccessDataSource1" > > > DataTextField="Vendor" > > > DataValueField="VendorID" > > > > onselectedindexchanged="DropDownList1_SelectedIndexChanged"> > > > </asp:DropDownList> > > > <asp:AccessDataSource ID="AccessDataSource1" > > > runat="server" > > > DataFile="~/App_Data/courses.mdb" > > > SelectCommand="SELECT * FROM [tblVendors] ORDER BY > > > [Vendor]"> > > > </asp:AccessDataSource> > > > </HeaderTemplate> > > > <ItemTemplate> > > > <asp:Label ID="Label1" runat="server" Text='<%# > > > Bind("Vendor") %>'></asp:Label> > > > </ItemTemplate> > > > </asp:TemplateField> > > > <asp:BoundField DataField="BasicCourseName" > > > HeaderText="BasicCourseName" > > > SortExpression="BasicCourseName" /> > > > </Columns> > > > </asp:GridView> > > > <asp:AccessDataSource ID="AccessDataSource1" runat="server" > > > DataFile="~/App_Data/courses.mdb" > > > SelectCommand="SELECT * FROM > > > [qryCoursesByVendors]"></asp:AccessDataSource> > > > </form> > > > </body> > > > </html> > > > > I don't know where to attach the code behind the form; on the dropdown list > > > changed event, or the page load event, or...? I am sorry if this is stupid, > > > but I can't seem to get it. Here is what I have in the code behind the form: > > > > Protected Sub DropDownList1_SelectedIndexChanged(ByVal sender As Object, > > > ByVal e As System.EventArgs) > > > > Dim ddlVendor As DropDownList > > > ddlVendor = Me.GridView1.FindControl("DropDownList1") > > > AccessDataSource1.FilterExpression = "VendorID = " & > > > ddlVendor.SelectedItem.Text > > > > End Sub > > > > I have also experimented with: > > > ddlVendor = CType(GridView1.TemplateControl.FindControl("DropDownList1"), > > > DropDownList) > > > > I get the following error message: > > > > Description: An unhandled exception occurred during the execution of the > > > current web request. Please review the stack trace for more information about > > > the error and where it originated in the code. > > > > Exception Details: System.NullReferenceException: Object reference not set > > > to an instance of an object. > > > > Source Error: > > > > Line 36: Dim ddlVendor As DropDownList > > > Line 37: ddlVendor = Me.GridView1.FindControl("DropDownList1") > > > Line 38: AccessDataSource1.FilterExpression = "VendorID = " & > > > ddlVendor.SelectedItem.Text > > > Line 39: End If > > > > Is there any way to implement this type of thing, or is this a nightmare? I > > > am a beginning programmer, and I've already spent many days making only > > > incremental advances. > > > > thanks in advance for your help and support. > > > > mike hi , I am also doing the same thing in C#.net i had the error at the line DropDownList ddl1 = GridView1.HeaderRow.FindControl("ddl"); the error is Cannot implicitly convert type 'System.Web.UI.Control' to 'System.Web.UI.WebControls.DropDownList'. An explicit conversion exists (are you missing a cast?) Please reply me Sagar Kandekar
Hi, I'm sorry, I don't know C#...but the code I posted does work for me in
Visual Basic. I have heard there is a website that will convert visual basic to C#; maybe google it? good luck! [quoted text, click to view] "sskandekar@gmail.com" wrote:
> On Feb 21, 3:46 am, Mike <M...@discussions.microsoft.com> wrote: > > OK OK for what it's worth, here is the result of my stupid 25 hours of > > digging...sheesh! > > > > This does not throw an error: > > > > Dim ddlVendorFilter As DropDownList = > > gvCourses.HeaderRow.FindControl("ddlVendor") > > > > I have not tried including it in a Ctype expression, and I'm not sure it's > > necessary... > > > > The key is including the HeaderRow in the code, because the control is in > > the headerRow...I guess this is "duh!" for many of you, but perhaps it may > > help a fool like me save several days of frustration...good luck! > > > > "Mike" wrote: > > > A little more update, I've also tried: > > > > > Dim ddlVendorFilter As DropDownList = > > > CType(gvCourses.FindControl("ddlVendor"), DropDownList) > > > > > MsgBox("ddlVendor Selected Value is" & > > > ddlVendorFilter.SelectedValue) 'Returns error > > > > > "Mike" wrote: > > > > > > Hello, > > > > > > I have a gridview that I want to basically convert to behavior like Excel > > > > autofilter. I have created a dropdown list and put it into the header of the > > > > gridview, but I can't seem to reference it correctly. I have been trolling > > > > through the net and ms references for hours but I can't get it straight. > > > > > > Here is the html code: > > > > > > <%@ Page Language="VB" AutoEventWireup="false" > > > > CodeFile="datagridtest4.aspx.vb" Inherits="datagridtest4" %> > > > > > > <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" > > > > "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> > > > > > > <html xmlns="http://www.w3.org/1999/xhtml"> > > > > <head runat="server"> > > > > <title>Untitled Page</title> > > > > </head> > > > > <body> > > > > <form id="form1" runat="server"> > > > > <div> > > > > > > </div> > > > > <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" > > > > DataSourceID="AccessDataSource1"> > > > > <Columns> > > > > <asp:TemplateField HeaderText="Vendor" SortExpression="Vendor"> > > > > <EditItemTemplate> > > > > <asp:TextBox ID="TextBox1" runat="server" Text='<%# > > > > Bind("Vendor") %>'></asp:TextBox> > > > > </EditItemTemplate> > > > > <HeaderTemplate> > > > > <asp:DropDownList ID="DropDownList1" runat="server" > > > > AutoPostBack="True" > > > > DataSourceID="AccessDataSource1" > > > > DataTextField="Vendor" > > > > DataValueField="VendorID" > > > > > > onselectedindexchanged="DropDownList1_SelectedIndexChanged"> > > > > </asp:DropDownList> > > > > <asp:AccessDataSource ID="AccessDataSource1" > > > > runat="server" > > > > DataFile="~/App_Data/courses.mdb" > > > > SelectCommand="SELECT * FROM [tblVendors] ORDER BY > > > > [Vendor]"> > > > > </asp:AccessDataSource> > > > > </HeaderTemplate> > > > > <ItemTemplate> > > > > <asp:Label ID="Label1" runat="server" Text='<%# > > > > Bind("Vendor") %>'></asp:Label> > > > > </ItemTemplate> > > > > </asp:TemplateField> > > > > <asp:BoundField DataField="BasicCourseName" > > > > HeaderText="BasicCourseName" > > > > SortExpression="BasicCourseName" /> > > > > </Columns> > > > > </asp:GridView> > > > > <asp:AccessDataSource ID="AccessDataSource1" runat="server" > > > > DataFile="~/App_Data/courses.mdb" > > > > SelectCommand="SELECT * FROM > > > > [qryCoursesByVendors]"></asp:AccessDataSource> > > > > </form> > > > > </body> > > > > </html> > > > > > > I don't know where to attach the code behind the form; on the dropdown list > > > > changed event, or the page load event, or...? I am sorry if this is stupid, > > > > but I can't seem to get it. Here is what I have in the code behind the form: > > > > > > Protected Sub DropDownList1_SelectedIndexChanged(ByVal sender As Object, > > > > ByVal e As System.EventArgs) > > > > > > Dim ddlVendor As DropDownList > > > > ddlVendor = Me.GridView1.FindControl("DropDownList1") > > > > AccessDataSource1.FilterExpression = "VendorID = " & > > > > ddlVendor.SelectedItem.Text > > > > > > End Sub > > > > > > I have also experimented with: > > > > ddlVendor = CType(GridView1.TemplateControl.FindControl("DropDownList1"), > > > > DropDownList) > > > > > > I get the following error message: > > > > > > Description: An unhandled exception occurred during the execution of the > > > > current web request. Please review the stack trace for more information about > > > > the error and where it originated in the code. > > > > > > Exception Details: System.NullReferenceException: Object reference not set > > > > to an instance of an object. > > > > > > Source Error: > > > > > > Line 36: Dim ddlVendor As DropDownList > > > > Line 37: ddlVendor = Me.GridView1.FindControl("DropDownList1") > > > > Line 38: AccessDataSource1.FilterExpression = "VendorID = " & > > > > ddlVendor.SelectedItem.Text > > > > Line 39: End If > > > > > > Is there any way to implement this type of thing, or is this a nightmare? I > > > > am a beginning programmer, and I've already spent many days making only > > > > incremental advances. > > > > > > thanks in advance for your help and support. > > > > > > mike > > hi , > I am also doing the same thing in C#.net > i had the error at the line > DropDownList ddl1 = GridView1.HeaderRow.FindControl("ddl"); > the error is > Cannot implicitly convert type 'System.Web.UI.Control' to > 'System.Web.UI.WebControls.DropDownList'. An explicit conversion > exists (are you missing a cast?) > > Please reply me > Sagar Kandekar >
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