I am trying to implement a gridview with checkbox column on asp.net (VB). when the user checks checkbox and click delete button, it should access database and delete all checked item.
I have already tried numerous googled solution and never worked for me. here is short scenario
on my aspx page:
1)search by id text box, when user enter ID and click search button, the below table is displayed
<asp:GridView ID="MyGridView" runat="server">
<Columns>
<asp:TemplateField headertext="Name">
<ItemTemplate>
<asp:Label id="namelbl"
text='<%# Eval("name")%>' runat="server"/>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Delete Now?">
<ItemTemplate>
<asp:CheckBox Enabled="true" ID="chkStatus" runat="server" />
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
after data is displayed, user checks the desired checkbox and click delete button, then the code behind is run
Protected Sub DelSelected(ByVal sender As Object, ByVal e As System.EventArgs)
Dim idList as ArrayList = new ArrayList()
For Each row As GridViewRow In MyGridView.Rows
Dim selectcb As CheckBox = CType(row.FindControl("chkStatus"), CheckBox)
If (selectcb.Checked) Then
'put into delete list
Trouble starts here, selectcb checkbox is always false
How could that happen, any idea would be appreciated
Thanks
you must bind your data only when no IsPostback in order to persist your checkbox selected, and no reset
If(! IsPostBack)
{
Bind();
}
Related
I have a gridview loaded from a database with a checkbox in the first column. What I want is that when clicking on any row the grid will be filtered to show only the rows in which the value of the second cell is the same as the one I clicked on (having the option to select more rows with that value). Removing the checks he would reload all the information again. I tried doing it using the OnChecked event, but due to AutoPostBack it filters but loses the value of the checkbox checked. What is the best way to do what I want? I hope I have been explicit. Thank you
asp:GridView ID="gridview" runat="server" AutoGenerateColumns="false" DataKeyNames="Id">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<asp:CheckBox ID="chkRow" OnCheckedChanged="chkRow_CheckedChanged" AutoPostBack="true" runat="server" />
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="Document" ItemStyle-Width="10%" HeaderText="Documento" />
<asp:BoundField DataField="Entidad" ItemStyle-Width="55%" HeaderText="Entidad" />
</Columns>
For Each row As GridViewRow In gvEncomendasPendentes.Rows
If row.RowType = DataControlRowType.DataRow Then
Dim chkRow As CheckBox = TryCast(row.Cells(0).FindControl("chkRow"), CheckBox)
If chkRow.Checked Then
'Bind with filter
End If
End If
Next
Does the table display the entire dataset at all times? If so, I'd check into client-side filtering (JavaScript). Not having the round trip to the server/database would make your page a lot more responsive.
But assuming that's not the case, and to actually answer the posted question, here's how I'd approach it in the VB.Net Code. Try changing the Change Event like this:
Protected Sub chkRow_CheckedChanged (sender as object, e As EventArgs)
Dim chk As CheckBox = DirectCast(sender, CheckBox)
dim grv As GridRowView = DirectCast(chk.NamingContainer, GridRowView)
dim hdn AS HiddenField = grv.FindControl("hdnFieldWithValue")
If chk.Checked then
AddValueToFilerList(hdn.Value)
Else
RemoveValueFromFilterList(hdn.Value)
End If
BindGridView()
End Sub
Your way does work, but that has a Log(N) time on processing, as it needs to look at every row in the grid. The above way will KNOW which checkbox was checked, and deal with it appropriately.
And this small change to the markup:
<asp:hiddenField runat='server' id='hdnFilterList' />
<asp:GridView ID="gridview" runat="server" AutoGenerateColumns="false" DataKeyNames="Id">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<asp:CheckBox ID="chkRow" OnCheckedChanged="chkRow_CheckedChanged" AutoPostBack="true" runat="server" checked='<%# CheckValueInFilterList(Eval("Entidad")) %>' />
<asp:hiddenField id="hdnFieldWithValue" runat="server" value='<%# Eval("Entidad")' />
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="Document" ItemStyle-Width="10%" HeaderText="Documento" />
<asp:BoundField DataField="Entidad" ItemStyle-Width="55%" HeaderText="Entidad" />
</Columns>
You'll also a function something like this:
Protected Function CheckValueInFilterList(input as string) as boolean
Return MyListOfFilterItems.Contains(input)
End Function
The purpose of that would be to see if the input is contained in your list of filters you're applying to your query and returning true/false depending on that.
Which is directly related to why you're not retaining a check in the checkboxes between postbacks. Since you're rebinding the grid, the existing form state is thrown away in favor of the values from the bind. Since your markup lacked a setter for the checkbox's checked state in the databind, it always resorted to false.
I also added a hidden field to the Markup which would contain the filter list as some type of serialized string (JSON, XML, etc). I'd read it from that field on the Page Load where IsPostBack is True, and always write the list to it in the PreRender event. The point is to just have that passed back and forth through the posted form state so that you can remember them between postbacks.
Maintaining that list of filters in a control outside of the gridview as described does add a bit of overhead in the data that is sent to/from the server on roundtrips. But I wouldn't expect that to a large amount, and would expect a preformance increase due to not having to iterate through the entire gridview item list on every postback.
I've run into a wall and could use some advice. I have a gridview that contains a "Details" hyperlink on each row. While I am in edit mode (inline), I want to disable the details link. I thought this would be simple, but I can't seem to make it work. I had assumed (wrongly) that I could do something like:
Dim lnkDetails As HyperLink = CType(e.Row.FindControl("lnkDetails"), HyperLink)
lnkDetails.Enabled = False
The problem here, as I found out, is the "e As GridViewEditEventArgs" part of my Sub doesn't include "Row".
Here is the relevant code:
Protected Sub gvCurRecords_RowEditing(ByVal sender As Object, ByVal e As GridViewEditEventArgs)
' Make the GridView control into edit mode for the selected row.
gvCurRecords.EditIndex = e.NewEditIndex
' Rebind the GridView control to show data in edit mode.
BindGridView()
' Hide the Add button.
lbtnAdd.Visible = False
End Sub
HTML (Only the relevant column):
<asp:GridView ID="gvCurRecords" CellPadding="4" DataSourceId="SqlDataSource1"
Autogeneratecolumns="false" AutoGenerateEditButton="true"
AutoGenerateDeleteButton="true" OnRowEditing="gvCurRecords_RowEditing"
OnRowCancelingEdit="gvCurRecords_RowCancelingEdit"
OnRowUpdating="gvCurRecords_RowUpdating" DataKeyNames="eventID"
OnRowDataBound="gvCurRecords_RowDataBound"
OnPageIndexChanging="gvCurRecords_PageIndexChanging" runat="server">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<asp:HyperLink ID="lnkDetails" runat="server" Text='Details' NavigateUrl='<%#FormatUrl(CInt(Eval("EventID")))%>' />
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:Gridview>
Any help would be greatly appreciated. Thanks.
Use the edit template to define a label instead of a hyperlink:
<EditItemTemplate>
<asp:Label ID="lbDetails" runat="server" Text='something else' />
</EditItemTemplate>
I'm retrofitting an older web forms site with Model Binding using asp.net 4.5.
In a DetailsView I have a drop down list that allows selection of a particular 'client' and another that allows selection of a particular 'project' that belongs to that client. So the drop down for project has to be filtered on the client number and if the user changes the client selection, I want to filter the project list by client number.
I couldn't figure out how to get the SelectedIndexChanged method on the client ddl to fire the Select method for the Project, so I concluded the only way to do it was to filter the project ddl by client number in all cases. I am getting an error message when the client selection is made:
NullReferenceException was Unhandled by User Code
which point in my aspx directly to the ddl for Projects.
This is an abbreviated version of the details view, you can see both the clients ddl and the projects ddl (I am operating in Edit mode):
<asp:DetailsView ID="AdministratorDetailsView" runat="server" AutoGenerateRows="False"
DataKeyNames="AdministratorNumber" ItemType="BusinessLogic.Administrator"
Width="99%"
SelectMethod="AdministratorDetailsView_GetItem"
UpdateMethod="AdministratorDetailsView_UpdateItem"
DeleteMethod="AdministratorDetailsView_DeleteItem"
FieldHeaderStyle-Width="30%" EditRowStyle-Width="99%"
InsertRowStyle-Width="70%" RowStyle-Width="99%" CssClass="admin"
AutoGenerateDeleteButton="true" AutoGenerateEditButton="true" >
<Fields>
<asp:TemplateField HeaderText="AdministratorCode" SortExpression="AdministratorCode">
<EditItemTemplate>
<asp:Label ID="AdministratorCode" Text="<%# Item.AdministratorCode%>" runat="server" />
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="AdministratorCode" Text="<%# Item.AdministratorCode%>" runat="server" />
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="ClientNumber" SortExpression="ClientNumber">
<EditItemTemplate>
<asp:DropDownList ID="ddClients" runat="server"
AutoPostBack="true"
DataTextField="ClientName" DataValueField="ClientNumber"
ItemType="BusinessLogic.Client"
SelectMethod="ddClients_GetList"
SelectedValue="<%# Item.ClientNumber%>"
OnSelectedIndexChanged="AdministratorDetailsView_ddlClients_SelectedIndexChanged"/>
</EditItemTemplate>
<ItemTemplate>
<asp:DropDownList ID="ddClients" runat="server" Enabled="false"
DataTextField="ClientName" DataValueField="ClientNumber"
ItemType="BusinessLogic.Client"
SelectMethod="ddClients_GetList"
SelectedValue="<%# Item.ClientNumber%>"/>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Projects" >
<EditItemTemplate>
<asp:DropDownList ID="ddProjects" runat="server" AutoPostBack="true"
DataTextField="ProjectName" DataValueField="ProjectNumber"
ItemType="BusinessLogic.Project"
SelectMethod="ddProjects_GetList"
SelectedValue="<%# Item.ProjectNumber%>" />
</EditItemTemplate>
<ItemTemplate>
<asp:DropDownList ID="ddProjects" runat="server" Enabled="false"
DataTextField="ProjectName" DataValueField="ProjectNumber"
ItemType="BusinessLogic.Project"
SelectMethod="ddProjects_GetList"
SelectedValue="<%# Item.ProjectNumber%>"/>
</ItemTemplate>
</asp:TemplateField>
</Fields>
</asp:DetailsView>
There are two SelectMethods, one for each drop down list, and a selectedindexchaneged method for clients:
Public Function ddClients_GetList() As List(Of BusinessLogic.Client)
Dim special As New List(Of Client)
special = CurrentClient.ClientList() 'add whole list
Dim NullClient As New Client()
NullClient.Load(0)
NullClient.ClientName = "<-Not Selected-->"
special.Add(NullClient) 'Had to have a client with 0 in the list since most admins don't have anything but 0 inthis field
Return special
End Function
Public Function ddProjects_GetList(<Control("ddClients")> ByVal ClientNumber As Integer) As List(Of BusinessLogic.Project)
Dim special As New List(Of Project)
If ClientNumber = 0 Then
special = CurrentProject.ProjectList() 'add whole list, refine it if Clients Drop Down selected
Else
special = CurrentProject.ProjectList(ClientNumber) 'add whole list, refine it if Clients Drop Down selected
End If
Dim NullProject As New Project()
NullProject.Load(0)
NullProject.ProjectName = "<-Not Selected-->"
special.Add(NullProject) 'Had to have a Project with 0 in the list since most admins don't have anything but 0 inthis field
Return special
End Function
Protected Sub AdministratorDetailsView_ddlClients_SelectedIndexChanged(sender As Object, e As EventArgs)
Dim ddlProj As DropDownList
ddlProj = AdministratorDetailsView.FindControl("ddProjects")
ddlProj.ItemType = "BusinessLogic.Project"
ddlProj.DataBind()
End Sub
All is well until the user selects a different client which triggers the SelectIndexChanged event and then we get to the DataBind(), where we get the null exception (ddlProj is found).
Need some ideas on how to refresh the projects list based on the new client selection.
How do I force ddProjects to run its SelectMethod again, to avoid the null reference and reload the control?
Turns out this issue is not unique to ModelBinding, but is a General WebForms Issue.
You cannot have cascading dropdowns within another data control where they depend on each other unless you add a bit of code.
In my case, I was trying to bind both dropdowns to the underlying detailsview, and at the same time setting the selected values. Doesn't work because of timing. It seems right until you try to change the selection on the parent dropdown, and then you get null exception on the second because it is not yet loaded. It's all timing. If you try to work around it with saved values, it gets too messy.
My solution is, Bind another item to the underlying details view (you can make it hidden if you wish). Then add some code to keep it in sync with the actual value. DO NOT Bind SelectedValue on the secondary drop down , this is what causes the problem. Manage Selected Value in code using the added field.
<asp:DetailsView ID="AdministratorDetailsView" runat="server" AutoGenerateRows="False"
DataKeyNames="AdministratorNumber" ItemType="BusinessLogic.Administrator"
Width="99%" SelectMethod="AdministratorDetailsView_GetItem" UpdateMethod="AdministratorDetailsView_UpdateItem" DeleteMethod="AdministratorDetailsView_DeleteItem"
FieldHeaderStyle-Width="30%" EditRowStyle-Width="99%" InsertRowStyle-Width="70%" RowStyle-Width="99%" CssClass="admin" AutoGenerateDeleteButton="true" AutoGenerateEditButton="true"
>
<Fields>
<asp:TemplateField HeaderText="Client Name" SortExpression="ClientName">
<EditItemTemplate><asp:DropDownList ID="ddClients" runat="server" AutoPostBack="true" DataTextField="ClientName" DataValueField="ClientNumber" ItemType="BusinessLogic.Client" SelectMethod="ddClients_GetList" SelectedValue="<%# Item.ClientNumber%>" OnDataBound="ddClients_DataBound" OnSelectedIndexChanged="AdministratorDetailsView_ddlClients_SelectedIndexChanged" /> </EditItemTemplate>
<ItemTemplate><asp:DropDownList ID="ddClients" runat="server" Enabled="false" DataTextField="ClientName" DataValueField="ClientNumber" ItemType="BusinessLogic.Client" SelectMethod="ddClients_GetList" SelectedValue="<%# Item.ClientNumber%>"/></ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText ="Project Number" >
<EditItemTemplate><asp:Label ID="ProjectNumberLabel" runat="server" Text="<%# BindItem.ProjectNumber%>"></asp:Label></EditItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Project Name" SortExpression="ProjectNumber">
<EditItemTemplate><asp:DropDownList ID="ddProjects" runat="server" AutoPostBack="true" DataTextField="ProjectName" DataValueField="ProjectNumber" ItemType="BusinessLogic.Project" SelectMethod="ddProjects_GetList" OnDataBound="ddProjects_DataBound" OnSelectedIndexChanged="ddProjects_SelectedIndexChanged" />
</EditItemTemplate>
<ItemTemplate><asp:DropDownList ID="ddProjects" runat="server" Enabled="false" DataTextField="ProjectName" DataValueField="ProjectNumber" ItemType="BusinessLogic.Project" SelectMethod="ddProjects_GetList" SelectedValue="<%# Item.ProjectNumber%>" />
</ItemTemplate>
</asp:TemplateField>
</asp:DetailsView>
And in the code behind, not how we set and get the value of the bound projectnumber:
Protected Sub AdministratorDetailsView_ddlClients_SelectedIndexChanged(sender As Object, e As EventArgs)
''If this selection changes we need to change some flags and perhaps theProject ddl
''This causes null exception for Project ddl, can't figure out how to get it to reload. Tried DataBind(), same effect as having a ValueProvider in the parameters to the Select
Dim ProjectNumberLabel As Label = AdministratorDetailsView.FindControl("ProjectNumberLabel")
ProjectNumberLabel.Text = "0" 'Synchronize to no selection
Dim ddProjects As New DropDownList
ddProjects = AdministratorDetailsView.FindControl("ddProjects") 'Have to use Find Control because ddl is buried in DetailsView
ddProjects.SelectedValue = 0 'Cause it to read Select an Item
ddProjects.DataBind() 'Rebinding it causes the SelectMethod to run.
End Sub
Protected Sub ddProjects_DataBound(sender As Object, e As EventArgs)
'Because of the problem with cascading references, we had to remove the SelectValue declaration from ddProjects.
'So we must make sure that once theddProjects is databound, it points to the selected value from the data
Dim ddlProjects As DropDownList
ddlProjects = AdministratorDetailsView.FindControl("ddProjects")
Dim ProjectNumberLabel As Label = AdministratorDetailsView.FindControl("ProjectNumberLabel")
ddlProjects.SelectedValue = CInt(ProjectNumberLabel.Text)
End Sub
Hope someone else sees this as useful. I couldn't find it anywhere.
Great posting, as I faced a similar conundrum and it made me think. I have done this before outside of the model-binding approach, and the solution is essentially the same, as described. I used a ListView, and added the method:
OnItemDataBound="lvWhatever_ItemDataBound"
to fire an event from which to go and get the relevant ID from another bound control in the list view data item:
if (e.Item.ItemType == ListViewItemType.DataItem)
{
// get the ID from from another control in this item record: lblItemID
ListViewDataItem lvdi = (ListViewDataItem)e.Item;
if (lvdi != null)
{
Label iID = (Label)lvdi.FindControl("lblItemID");
if (iID != null)
where lblItemID.Text contains the relevant ID. Then from that I can query to get the relevant list, and manually bind it to the DDL. Brilliant - thanks very much.
I have a GridView with a Checkbox on the first column:
<asp:GridView ID="dgNumeradores" runat="server" AutoGenerateColumns="False" CellPadding="4" DataKeyNames="ItemID">
<Columns>
<asp:TemplateField HeaderText="Seleccionar">
<ItemTemplate>
<asp:CheckBox runat="server" ID="chkChecked" />
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField HeaderText="Item" DataField="Description">
</asp:BoundField>
<asp:BoundField HeaderText="Plantilla" DataField="Template">
</asp:BoundField>
</Columns>
</asp:GridView>
Now in the code behind I try to update the Checked column on the DataTable acting as datasource for the GridView (since, as you can see above, the Checkbox column is not bound to the datasource for reasons you probably know.):
Protected Sub btnSave_Click(sender As Object, e As EventArgs) Handles btnSave.Click
Try
For Each dr As GridViewRow In Me.dgNumeradores.Rows
Me.itemsNumTable.Select("ItemID = '" & dgNumeradores.DataKeys(dr.RowIndex).Value & "'")(0)("Checked") = DirectCast(dr.Cells(0).FindControl("chkChecked"), CheckBox).Checked
Next
'Some more unimportant-for-this-question code
Catch ex As Exception
tableInfo.ShowError(ex.Message)
End Try
End Sub
The thing is that the Checkbox.Checked always returns False.
How can I get the checked state of the Checkboxes in this scenario? Or what would be the best approach into updating the aforementioned column?
P.S. Note that click on the checkboxes doesn't post back. Nothing happens on the page until the user clicks Save (and that is the intended behavior).
Are you binding the GridView in Page Load? If that is the case use IsPostBack
IF Not IsPostBack Then
DataBind()
End IF
Should you not have the AutoPostback property set to true?
<asp:CheckBox runat="server" ID="chkChecked" AutoPostback="true" />
I have two columns in my GridView. The first column contains filenames,
the second column contains Checkboxes. Once the user has selected an arbitrary
number of Checkboxes then by clicking a button the selected files can be
downloaded.
My markup is as follows
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False">
<Columns>
<asp:BoundField HeaderText="Available Schemas"
DataField="SchemaFileName"
SortExpression="UserId">
</asp:BoundField>
<asp:TemplateField HeaderText="Select Schema">
<ItemTemplate>
<asp:CheckBox runat="server" ID="SelectedFiles" checked= '<%# Eval("checkValue") %>'/>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
My CodeBehind part is as follows
protected void Page_Load(object sender, EventArgs e)
{
GenerateDownloadLinks();
if (!IsPostBack)
{
GridView1.DataSource = listOfData;
GridView1.DataBind();
}
}
listOfData is populated in GenerateDownloadLinks() and then it is bind to GridView1.
Once the user selected files and clicks download then my code loops through
the rows of the GridView and when the CheckBox is checked it updates the initially
false value of the data entry to make sure which files should be made available for
download.
protected void GetFiles_Click(object sender, EventArgs e)
{
int i = 0;
foreach (GridViewRow row in GridView1.Rows)
{
CheckBox chkRow = (row.Cells[1].FindControl("SelectedFiles") as CheckBox);
if (chkRow.Checked)
{
listOfData[i].CheckValue = true;
}
i++;
}
}
Gridview fills perfectly even when it is not binded in Page.IsPostBack block, but here checkbox will always return false.
Bind gridview in Page.IsPostBack, and it would run perfectly fine.
Use below code
IF Not IsPostBack Then
DataBind()
End IF
And then Checkbox.Checked will return true.
Here is the setup:
I programmatically populate my gridview using LINQ to SQL query. Then I enter the edit mode and want to replace some standard TextBox controls with DropDownLists like this:
'excerpt from GridView1_RowEditing
Dim ddlist1 As New DropDownList
Dim res1 = From items1 In mydb.Items
Select items1.Col10
ddlist1.DataSource = res1
ddlist1.DataBind()
GridView1.Rows.Item(0).Cells(1).Controls.Add(ddlist1)
At this moment I have my gridview showing standard textbox control and new DDList control (in the Column 1).
The problem is -- I cant read the value from DDList in the RowUpdating method. It seems like DDList control is not in the GridView1.Rows.Item(0).Cells(1).Controls collection.
RowUpdating method sees only standard TextBox control and can read it's value.
Any suggestions are welcome. I just don't understand something here :(
Use TemplateField, and then you can locate your dropdown using FindControl
<asp:GridView ID="GridView1" runat="server">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
</ItemTemplate>
<EditItemTemplate>
<asp:DropDownList ID="DropDownList1" runat="server">
</asp:DropDownList>
</EditItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
...
Protected Sub GridView1_RowUpdating(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewUpdateEventArgs) Handles GridView1.RowUpdating
Dim ddl = CType(GridView1.Rows(e.RowIndex).Cells(1).FindControl("DropDownList1"), DropDownList)
End Sub