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Retrieve value from DropDownList in nested GridView on RowCommand

I have a nested GridView(GvMP_Summary_Items). Each row contains a DropDownList. The DropDownList is bounded on the RowDataBound event of the nested GridView.
Each row also contains 1 Button. Upon pressing this button on the RowCommand event, I would like to find the current selected value of the DropDownList so I can use it further on in the code.
The code I have will only get the default value of the DropDownList on each row, which is currently set at 0 for each row.
Below is the RowCommand Event:
Protected Sub GvMP_Summary_Items_RowCommand(sender As Object, e As GridViewCommandEventArgs)
Dim lb As ImageButton = CType(e.CommandSource, ImageButton)
Dim gvRow As GridViewRow = lb.BindingContainer //Getting current row to get index
Dim GvMP_Summary_Items As GridView = CType(gvRow.FindControl("GvMP_Summary_Items"), GridView)
Dim intMPItem_Qty As Integer = CType(gvRow.FindControl("cboMPItem_Qty"), DropDownList).SelectedValue
Dim strMPItem_Qty As String = CType(gvRow.FindControl("txtMPItem_Qty"), TextBox).Text
End Sub
I have even included a TextBox in the GridView row which default value is empty "". Although on the row if something is entered the on RowCommand event brings back the value with a comma(,) in front of it.
This proves that I am picking up the correct row and can retrieve a value from a TextBox but not a DropDownList.
Is there something I am missing? Why can I return a value entered in a TextBox but not the selected value of a DropDownList? Also why the comma(,) in front of the TextBox value?
Note: In above case code has been written using VB so answers in VB over C# but I can accept both.

This can be done very easily by casting the CommandSource of the RowCommand back to a button and then get the correct row from that. Once you have the row you can use FindControl to locate the DropDownList. This works on every level of nested items and also on the top Control.
VB
Protected Sub GMP_Summary_Items_RowCommand(ByVal sender As Object, ByVal e As GridViewCommandEventArgs)
'cast the commandsource back to a button
Dim btn As Button = CType(e.CommandSource,Button)
'get the current gridviewrow from the button namingcontainer
Dim row As GridViewRow = CType(btn.NamingContainer,GridViewRow)
'use findcontrol to locate the dropdownlist in that row
Dim ddl As DropDownList = CType(row.FindControl("cboMPItem_Qty"),DropDownList)
'show the selected value of the dropdownlist
Label1.Text = ddl.SelectedValue
End Sub
Code was translated from C# with a code translator, so it may not be 100% accurate.
C#
protected void GMP_Summary_Items_RowCommand(object sender, GridViewCommandEventArgs e)
{
//cast the commandsource back to a button
Button btn = e.CommandSource as Button;
//get the current gridviewrow from the button namingcontainer
GridViewRow row = btn.NamingContainer as GridViewRow;
//use findcontrol to locate the dropdownlist in that row
DropDownList ddl = row.FindControl("cboMPItem_Qty") as DropDownList;
//show the selected value of the dropdownlist
Label1.Text = ddl.SelectedValue;
}
You do need to bind data to the GridView and the DropDownLists in an
IsPostBack check, otherwise the data will be rebound to the DDL on every PostBack and the selected value is lost

Important things:
Bind parent GridView in Page_Load method
Bind child GridView in parent GridView 's RowDataBound event
Bind DropDownList in child GridView 's RowDataBound event
Add CommandName to the Button which is inside child GridView
Finally, in RowCommand event of child GridView
Get child GridView 's row
Then find all controls inside child GridView from child GridView 's row
I'm not so aware of VB.NET so I have added an example (C#) of Nested GridView with RowCommand event (hope OP can use it in VB.NET):
HTML code (.Aspx):
<form id="form1" runat="server">
<asp:GridView ID="GridView_Outer" OnRowDataBound="GridView_Outer_RowDataBound" AutoGenerateColumns="false" runat="server">
<Columns>
<asp:TemplateField HeaderText="Outer Column1">
<ItemTemplate>
<asp:Label ID="Label_Outer" runat="server" Text='<%# Eval("Label_Outer") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Outer Column2">
<ItemTemplate>
<asp:GridView ID="GridView_Inner" OnRowDataBound="GridView_Inner_RowDataBound" OnRowCommand="GridView_Inner_RowCommand" AutoGenerateColumns="false" runat="server">
<Columns>
<asp:TemplateField HeaderText="Inner Column1">
<ItemTemplate>
<asp:Label ID="Label_Inner" runat="server" Text='<%# Eval("Label_Inner") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Inner Column2">
<ItemTemplate>
<asp:TextBox ID="TextBox_Inner" Text='<%# Eval("TextBox_Inner") %>' runat="server"></asp:TextBox>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Inner Column3">
<ItemTemplate>
<asp:DropDownList ID="DropDownList_Inner" runat="server"></asp:DropDownList>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Inner Column4">
<ItemTemplate>
<asp:Button ID="Button_Inner" runat="server" CommandName="BtnInnerCmd" Text="Inner Button" />
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
<br />
<asp:Label ID="Label_Result" runat="server"></asp:Label>
</form>
Code-Behind (.Aspx.cs):
DataTable TempDT = new DataTable();
protected void Page_Load(object sender, EventArgs e)
{
CreateDataTable();
if (!IsPostBack)
{
GridView_Outer.DataSource = TempDT;
GridView_Outer.DataBind();
}
}
// create DataTable
public void CreateDataTable()
{
TempDT = new DataTable();
TempDT.Columns.Add("Label_Outer");
TempDT.Columns.Add("Label_Inner");
TempDT.Columns.Add("TextBox_Inner");
TempDT.Rows.Add("OuterLabel", "InnerLabel", "");
TempDT.Rows.Add("OuterLabel", "InnerLabel", "");
// store DataTable into ViewState to prevent data loss on PostBack
ViewState["DT"] = TempDT;
}
// Calls Outer GridView on Data Binding
protected void GridView_Outer_RowDataBound(object sender, GridViewRowEventArgs e)
{
// check if gridview row is not in edit mode
if (e.Row.RowType == DataControlRowType.DataRow)
{
// Get Outer GrridView 's controls
Label Label_Outer = (Label)e.Row.FindControl("Label_Outer");
GridView GridView_Inner = (GridView)e.Row.FindControl("GridView_Inner");
// get DataTable from ViewState and set to Inner GridView
GridView_Inner.DataSource = (DataTable)ViewState["DT"];
GridView_Inner.DataBind();
}
}
// Calls Inner GridView on Data Binding
protected void GridView_Inner_RowDataBound(object sender, GridViewRowEventArgs e)
{
// check if gridview row is not in edit mode
if (e.Row.RowType == DataControlRowType.DataRow)
{
// Get Outer GrridView 's controls
DropDownList DropDownList_Inner = (DropDownList)e.Row.FindControl("DropDownList_Inner");
// Create a DataTable to Bind data for DropDownlist
DataTable TempDDLDT = new DataTable();
TempDDLDT.Columns.Add("ItemText");
TempDDLDT.Columns.Add("ItemValue");
TempDDLDT.Rows.Add("ItemText1", "ItemValue1");
TempDDLDT.Rows.Add("ItemText2", "ItemValue2");
// bind DataTable to the DropDownList
DropDownList_Inner.DataSource = TempDDLDT;
DropDownList_Inner.DataTextField = "ItemText";
DropDownList_Inner.DataValueField = "ItemValue";
DropDownList_Inner.DataBind();
}
}
// Calls when Inner GridView 's button clicked
protected void GridView_Inner_RowCommand(object sender, GridViewCommandEventArgs e)
{
// get Inner GridView 's clicked row
GridViewRow InnerGridViewRow = (GridViewRow)(((Control)e.CommandSource).NamingContainer);
// get Inner GridView 's controls from clicked row
TextBox TextBox_Inner = (TextBox)InnerGridViewRow.FindControl("TextBox_Inner");
DropDownList DropDownList_Inner = (DropDownList)InnerGridViewRow.FindControl("DropDownList_Inner");
// check if correct button is clicked
if (e.CommandName == "BtnInnerCmd")
{
string DropDownListValue = DropDownList_Inner.SelectedValue;
string TextBoxValue = TextBox_Inner.Text;
Label_Result.Text = "DropDownList 's Selected Value is " + DropDownListValue +
"<br />TextBox 's Entered Value is " + TextBoxValue;
}
}
Demo Image:
Note: Above DropDownList selects Selected Value not Text.

Run an event when Checkbox is Checked/Unchecked Gridview C#

I have a Gridview that has 4 columns. All in ItemTemplate One column is a CheckBox. This Gridview is binded to a datasource. What I want to do is when the Checkbox is checked update the database with the bit value '1' and if I uncheck the Checkbox to do the same but '0'.
I already know my SQL code to update the database, but I am not sure how to run the event so that it looks at the current row the checkbox is on in the gridview.
Here is the CheckBox Column.
<asp:TemplateField HeaderText="Pick" ItemStyle-CssClass="hrGrid" HeaderStyle-CssClass="hdrHrBase">
<ItemTemplate>
<asp:CheckBox id="cbViewCustomer" runat="server" OnCheckedChanged="ViewCustomer" onAutoPostBack="true" Checked='<%#(Eval("chosen"))%>'/>
</ItemTemplate>
</asp:TemplateField>
Do I use EventArgs like this:
The problem with this is it updates the database but all the rows.
What I am trying to do is update only the current row that is in the Gridview. I am just not sure where to go from here.
protected void ViewCustomer(object sender, EventArgs e)
{
string SelectCustomer = "UPDATE tblcustomer Set chosen ='0'";
NpgsqlCommand changedata = new NpgsqlCommand(SelectCustomer, con);
con.Open();
changedata.ExecuteNonQuery();
con.Close();
}
Or should I be doing something different?

You can do this with OnRowCommand event of gridview like this:-
Associate a RowCommand event with your gridview:-
<asp:GridView ID="mygridview" runat="server" OnRowCommand="mygridview_OnRowCommand">
Next, associate a CommandName & CommandArgument to your checkbox:-
<asp:TemplateField HeaderText="Pick" ItemStyle-CssClass="hrGrid" >
<ItemTemplate>
<asp:CheckBox id="cbViewCustomer" runat="server" Checked='<%#(Eval("chosen"))%>'
CommandName="myCheckbox" CommandArgument="<%# Container.DataItemIndex %>"/>
</ItemTemplate>
</asp:TemplateField>
In the code behind handle the event:-
protected mygridview_OnRowCommand (object sender, GridViewCommandEventArgs e)
{
if(e.CommandName == "myCheckbox")
{
int rowIndex = Convert.ToInt32(e.CommandArgument);
GridViewRow row = mygridview.Rows[rowIndex];
bool ischecked = (row.FindControl("cbViewCustomer") as CheckBox).Checked;
}
}
You can also do it with checbox checked event, but if you have multiple controls then fire the gridview command event instead of individual events.

how to get value of a template field label of a gridview, getting error Object reference not set to an instance of an object

While getting the value I'm getting Object reference not set to an instance of an object. how to get labeled label value in code behind. How to get the value in custom event
<asp:GridView runat="server" ID="gridviewQuoteDetails" EmptyDataText="No records Found..." AutoGenerateEditButton="false" OnRowEditing="gridviewQuoteDetails_RowEditing" OnRowUpdating="gridviewQuoteDetails_RowUpdating" DataKeyNames="id" AutoGenerateColumns="false">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<a href='Quote.aspx?val=<%#Eval("id")%>'>
<asp:Label ID="lblid" runat="server" Text='<%#Eval ("id")%>'></asp:Label>
</a>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField>
<ItemTemplate>
<asp:LinkButton ID="LinkButton1" Text="Edit" runat="server" CommandName="Edit" />
</ItemTemplate>
<EditItemTemplate>
<asp:LinkButton ID="LinkButton2" Text="Update" runat="server" OnClick="OnUpdate" />
</EditItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
code behind
protected void OnUpdate(object sender, EventArgs e)
{
string qouteid = ((Label)gridviewQuoteDetails.FindControl("lblid")).Text;
GridViewRow row = (sender as LinkButton).NamingContainer as GridViewRow;
string id = (row.Cells[0].Controls[0] as TextBox).Text;
string Description = (row.Cells[1].Controls[0] as TextBox).Text;
}

Gridview is a collection of rows right, but you are trying to search the control directly within the gridview thus ((LinkButton)gridviewQuoteDetails.FindControl("lbllnknm")) will be null and when you are trying to access the Text property of LinkButton you are getting NRE error.
You need to loop through the rows of your gridview control to access each linkbutton present in each row like this:-
foreach (GridViewRow row in gridviewQuoteDetails.Rows)
{
LinkButton lbllnknm= row.FindControl("lbllnknm") as LinkButton;
}
But ideally you would not be needing this. I guess you are trying to get the value in OnRowEditing event handler. If that is the case then you can fetch the value of linkbutton like this:-
protected void gridviewQuoteDetails_RowEditing(object sender, GridViewUpdateEventArgs e)
{
string qouteid = ((Label)gridviewQuoteDetails.Rows[e.NewEditIndex]
.FindControl("lbllnknm")).Text;
}
Update 2:
As per your comment you are trying to access the LinkButton text on click of LinkButton itself which means the event is raised by LinkButton itself. You can simply use the sender object like this:-
protected void OnUpdate(object sender, EventArgs e)
{
LinkButton LinkButton2 = sender as LinkButton;
GridViewRow row = LinkButton2.NamingContainer as GridViewRow; //Get the gridview row
Label lblid = row.FindControl("lblid") as Label;
string qouteid = lblid.Text;
}

Dynamically added controls missing during GridView RowUpdating

I have a GridView with a TemplateField column that I put PlaceHolder controls in. During the DataBound event for the GridView I dynamically add a few CheckBoxes to the PlaceHolder. That works fine and displays as expected.
My problem is that during the RowUpdating event the PlaceHolder contains no controls; my CheckBoxes are missing. I also noticed that they're missing during the RowEditing event.
I want to be able to get the values of the CheckBoxes during the RowUpdating event so I can save them to the database.
Here's some example code. I've trimmed out a lot to reduce size, but if you want to see specifics just ask and I'll be happy to add more.
HTML:
<asp:GridView ID="gridView" runat="server" AutoGenerateColumns="False"
ondatabound="gridView_DataBound" onrowupdating="gridView_RowUpdating"
onrowediting="gridView_RowEditing" DataKeyNames="ID">
<Columns>
<asp:TemplateField HeaderText="Countries">
<ItemTemplate>
<asp:PlaceHolder ID="countriesPlaceHolder" runat="server"></asp:PlaceHolder>
</ItemTemplate>
<EditItemTemplate>
<asp:PlaceHolder ID="countriesPlaceHolder" runat="server"></asp:PlaceHolder>
</EditItemTemplate>
</asp:TemplateField>
<asp:TemplateField ShowHeader="False">
<ItemTemplate>
<asp:LinkButton ID="editButton" runat="server" CommandName="Edit" Text="Edit"></asp:LinkButton>
</ItemTemplate>
<EditItemTemplate>
<asp:LinkButton ID="updateButton" runat="server" CommandName="Update" Text="Update"></asp:LinkButton>
</EditItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
Code behind:
// This method works fine, no obvious problems here.
protected void gridView_DataBound(object sender, EventArgs e)
{
// Loop through the Holidays that are bound to the GridView
var holidays = (IEnumerable<Holiday>)gridView.DataSource;
for (int i = 0; i < holidays.Count(); i++)
{
// Get the row the Holiday is bound to
GridViewRow row = gridView.Rows[i];
// Get the PlaceHolder control
var placeHolder = (PlaceHolder)row.FindControl("countriesPlaceHolder");
// Create a CheckBox for each country and add it to the PlaceHolder
foreach (Country country in this.Countries)
{
bool isChecked = holidays.ElementAt(i).Countries.Any(item => item.ID == country.ID);
var countryCheckBox = new CheckBox
{
Checked = isChecked,
ID = country.Abbreviation + "CheckBox",
Text = country.Abbreviation
};
placeHolder.Controls.Add(countryCheckBox);
}
}
}
protected void gridView_RowEditing(object sender, GridViewEditEventArgs e)
{
// EXAMPLE: I'm expecting checkBoxControls to contain my CheckBoxes, but it's empty.
var checkBoxControls = gridView.Rows[e.NewEditIndex].FindControl("countriesPlaceHolder").Controls;
gridView.EditIndex = e.NewEditIndex;
BindData();
}
protected void gridView_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
// EXAMPLE: I'm expecting checkBoxControls to contain my CheckBoxes, but it's empty.
var checkBoxControls = ((PlaceHolder)gridView.Rows[e.RowIndex].FindControl("countriesPlaceHolder")).Controls;
// This is where I'd grab the values from the controls, create an entity, and save the entity to the database.
gridView.EditIndex = -1;
BindData();
}
This is the article that I followed for my data binding approach: http://www.aarongoldenthal.com/post/2009/04/19/Manually-Databinding-a-GridView.aspx

You need to call your BindData() method on page load.
"Dynamic controls or columns need to be recreated on every page load, because of the way that controls work. Dynamic controls do not get retained so you have to reload them on every page postback; however, viewstate will be retained for these controls."
See Cells in gridview lose controls on RowUpdating event
Also in the article you linked, there is an ItemTemplate and an EditItemTemplace because they have different displays, i.e. read only and editable. Yours are the same so I think you could simplify your design:
<asp:GridView ID="gridView" runat="server" AutoGenerateColumns="False" DataKeyNames="ID" ondatabound="gridView_DataBound">
<Columns>
<asp:TemplateField HeaderText="Countries">
<ItemTemplate>
<asp:PlaceHolder ID="countriesPlaceHolder" runat="server"></asp:PlaceHolder>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField ShowHeader="False">
<ItemTemplate>
<asp:LinkButton ID="editButton" runat="server" Text="Edit" onclick="editButton_Click" ></asp:LinkButton>
<asp:LinkButton ID="updateButton" runat="server" Text="Update" onclick="updateButton_Click" ></asp:LinkButton>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
Code Behind:
protected void gridView_DataBound(object sender, EventArgs e)
{
// Loop through the Holidays that are bound to the GridView
var holidays = (IEnumerable<Holiday>)gridView.DataSource;
for (int i = 0; i < holidays.Count(); i++)
{
// Get the row the Holiday is bound to
GridViewRow row = gridView.Rows[i];
// Get the PlaceHolder control
var placeHolder = (PlaceHolder) row.FindControl("countriesPlaceHolder");
var countryCheckBox = new CheckBox
{
Checked = true,
ID = "auCheckBox",
Text = "Aus",
Enabled = false
};
placeHolder.Controls.Add(countryCheckBox);
var editButton = (LinkButton)row.FindControl("editButton");
editButton.CommandArgument = i.ToString();
var updateButton = (LinkButton)row.FindControl("updateButton");
updateButton.CommandArgument = i.ToString();
updateButton.Visible = false;
}
}
protected void editButton_Click(object sender, EventArgs e)
{
LinkButton editButton = (LinkButton) sender;
int index = Convert.ToInt32(editButton.CommandArgument);
GridViewRow row = gridView.Rows[index];
// Get the PlaceHolder control
LinkButton updateButton = (LinkButton)row.FindControl("updateButton");
updateButton.Visible = true;
editButton.Visible = false;
CheckBox checkbox = (CheckBox)row.FindControl("auCheckBox");
if (checkbox != null)
{
checkbox.Enabled = true;
// Get value and update
}
}
protected void updateButton_Click(object sender, EventArgs e)
{
LinkButton updateButton = (LinkButton)sender;
int index = Convert.ToInt32(updateButton.CommandArgument);
GridViewRow row = gridView.Rows[index];
// Get the PlaceHolder control
LinkButton editButton = (LinkButton)row.FindControl("updateButton");
editButton.Visible = true;
updateButton.Visible = false;
CheckBox checkbox = (CheckBox)row.FindControl("auCheckBox");
if (checkbox != null)
{
// Get value and update
checkbox.Enabled = false;
}
}
If you want to be it enabled from the get go, just remove the enabled checks and you can delete your edit button.
Hope that helps.

How to get the value?

I have a grid view which have checkbox. Now how to get its value on serverside.
<ItemTemplate>
<asp:CheckBox
ID="chkEditable" runat="server" AlternateText="Is Editable"
OnCheckedChanged="chkEditable_CheckedChanged"
AutoPostBack="true" Value='<%# Eval("PK_ID")%>' />
</ItemTemplate>

protected void chkEditable_OnCheckedChanged(object sender, EventArgs e)
{
GridViewRow gv = (GridViewRow)(((Control)sender).NamingContainer);
int pk = this.GridView1.DataKeys[gv.RowIndex].Value.ToString();
// Get the reference of this CheckBox
CheckBox chk = gv.FindControl("chkEditable") as CheckBox ;
//do stuff
}
Add the event handler manually to the code behind page