We Keep Coding

Binding GridView Columns to CheckBoxList Dynamically in C#

I want to bind only Table Columns to CheckBoxList and then the selected columns should be displayed in a GridView.
My code so far is:
public void BindCheckBoxList(DataSet ds)
{
int i = 0;
foreach (DataColumn dc in ds.Tables[0].Columns)
{
ListItem li = new ListItem(dc.ToString(), i.ToString());
CheckBoxList1.Items.Add(li); i++;
}
}

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" DataKeyNames="HobbyId">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<asp:CheckBox ID="chkSelect" runat="server" Checked='<%# Eval("IsSelected") %>' />
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="Hobby" HeaderText="Hobby" ItemStyle-Width="150px" />
</Columns>
</asp:GridView>
<br />
<asp:Button ID="btnSave" runat="server" Text="Save" OnClick="Save" />
in aspx.cs code
private void BindGrid()
{
string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
using (SqlConnection con = new SqlConnection(constr))
{
using (SqlCommand cmd = new SqlCommand("SELECT [HobbyId], [Hobby], [IsSelected] FROM Hobbies"))
{
using (SqlDataAdapter sda = new SqlDataAdapter())
{
cmd.Connection = con;
sda.SelectCommand = cmd;
using (DataTable dt = new DataTable())
{
sda.Fill(dt);
GridView1.DataSource = dt;
GridView1.DataBind();
}
}
}
}
}

protected void mainGridView_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow &&
(e.Row.RowState == DataControlRowState.Normal ||
e.Row.RowState == DataControlRowState.Alternate))
{
if (e.Row.Cells[1].FindControl("selectCheckbox") == null)
{
CheckBox selectCheckbox = new CheckBox();
//Give id to check box whatever you like to
selectCheckbox.ID = "newSelectCheckbox";
e.Row.Cells[1].Controls.Add(selectCheckbox);
}
}
}
i think you use this code.

Here a complete example to hide GridView Columns based on a CheckBoxList.
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
//fill the datatable from the database
DataTable dt = //fill the table here...
//bind the table to the grid
GridView1.DataSource = dt;
GridView1.DataBind();
//loop all the datatable columns to fill the checkboxlist
for (int i = 0; i < dt.Columns.Count; i++)
{
CheckBoxList1.Items.Insert(i, new ListItem(dt.Columns[i].ColumnName, dt.Columns[i].ColumnName, true));
}
}
}
protected void CheckBoxList1_TextChanged(object sender, EventArgs e)
{
//loop all checkboxlist items
foreach (ListItem item in CheckBoxList1.Items)
{
if (item.Selected == true)
{
//loop all the gridview columns
for (int i = 0; i < GridView1.Columns.Count; i++)
{
//check if the names match and hide the column
if (GridView1.HeaderRow.Cells[i].Text == item.Value)
{
GridView1.Columns[i].Visible = false;
}
}
}
}
}
And on the .aspx page
<asp:CheckBoxList ID="CheckBoxList1" runat="server" OnTextChanged="CheckBoxList1_TextChanged" AutoPostBack="true"></asp:CheckBoxList>
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false">
<Columns>
<asp:BoundField DataField="field01" HeaderText="Column A" />
<asp:BoundField DataField="field02" HeaderText="Column B" />
<asp:BoundField DataField="field03" HeaderText="Column C" />
<asp:BoundField DataField="field04" HeaderText="Column D" />
<asp:BoundField DataField="field05" HeaderText="Column E" />
</Columns>
</asp:GridView>
Note that AutoGenerateColumns is set to false. If they are auto-generated the columns are not part of the GridView Columns Collection.
And of course HeaderText="xxx" must match the column names from the database that are stored in the DataTable.

what is the command of select in grid view asp.net

I have a GridView called gridview1
What I want is that if the user select or click on specific row some action will happen.
For example I want to get the value from that row and store it in a new variable.
How can I do it? I'm confused about what I should do to get the value?
protected void GridView1_SelectedIndexChanging(object sender, GridViewSelectEventArgs e)
{
string stuId = ?
}

<asp:GridView ID="GridView1" runat="server" HeaderStyle-BackColor="#3AC0F2" HeaderStyle-ForeColor="White"
AutoGenerateColumns="false" OnSelectedIndexChanged = "OnSelectedIndexChanged">
<Columns>
<asp:BoundField DataField="Name" HeaderText="Name" ItemStyle-Width="150" />
<asp:TemplateField HeaderText="Country" ItemStyle-Width="150">
<ItemTemplate>
<asp:Label ID="lblCountry" runat="server" Text='<%# Eval("Country") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:ButtonField Text="Select" CommandName="Select" ItemStyle-Width="150" />
</Columns>
</asp:GridView>
<br />
<u>Selected Row Values: </u>
<br />
<br />
<asp:Label ID="lblValues" runat="server" Text=""></asp:Label>
aspx.cs code
protected void Page_Load(object sender, EventArgs e)
{
if (!this.IsPostBack)
{
DataTable dt = new DataTable();
dt.Columns.AddRange(new DataColumn[3] { new DataColumn("Id"), new DataColumn("Name"), new DataColumn("Country") });
dt.Rows.Add(1, "John Hammond", "United States");
dt.Rows.Add(2, "Mudassar Khan", "India");
dt.Rows.Add(3, "Suzanne Mathews", "France");
dt.Rows.Add(4, "Robert Schidner", "Russia");
GridView1.DataSource = dt;
GridView1.DataBind();
}
}
protected void OnSelectedIndexChanged(object sender, EventArgs e)
{
//Accessing BoundField Column
string name = GridView1.SelectedRow.Cells[0].Text;
//Accessing TemplateField Column controls
string country = (GridView1.SelectedRow.FindControl("lblCountry") as Label).Text;
lblValues.Text = "<b>Name:</b> " + name + " <b>Country:</b> " + country;
}
you simply copy and paste your issue is resolve.

you could use like this:
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns = "false"
OnRowCommand = "OnRowCommand">
<Columns>
<asp:ButtonField CommandName = "ButtonField" DataTextField = "StudID"
ButtonType = "Button"/>
</Columns>
</asp:GridView>
protected void OnRowCommand(object sender, GridViewCommandEventArgs e)
{
int index = Convert.ToInt32(e.CommandArgument);
GridViewRow gvRow = GridView1.Rows[index];
}

Sorting gridview column in asp.net

I have a gridview that loads data from database. The data is displayed in the gridview for the first time sorted by datetime. On one column of that gridview I want to allow sorting, for example on the main_post column. I had tried this, but the gridview still did not sort when I click the header of the column.
This is my front-end code for gridview:
<asp:DataGrid ID="Datagrid1" runat="server"
AllowPaging="True"
AllowSorting="True"
OnSorting="ComponentGridView_Sorting">
<Columns>
<asp:BoundColumn DataField="main_post" HeaderText="Header Post ID"
SortExpression="ComponentGridView_Sorting" />
</Columns>
</asp:DataGrid>
My back-end code:
protected void loadData()
{
DataTable dtTemp;
dtTemp = objDBInterface.getResults(strSQL);
Datagrid1.DataSource = dtTemp;
Datagrid1.DataBind();
ViewState["dtbl"] = dtTemp;
}
protected void ComponentGridView_Sorting(object sender, GridViewSortEventArgs e)
{
DataTable dataTable = ViewState["dtbl"] as DataTable;
if (dataTable != null)
{
DataView dataView = new DataView(dataTable);
dataView.Sort = e.SortExpression + " " + ConvertSortDirection(e.SortDirection);
Datagrid1.DataSource = dataView;
Datagrid1.DataBind();
}
}
private string ConvertSortDirection(SortDirection sortDirection)
{
string newSortDirection = String.Empty;
switch (sortDirection)
{
case SortDirection.Ascending:
newSortDirection = "ASC";
break;
case SortDirection.Descending:
newSortDirection = "DESC";
break;
}
return newSortDirection;
}
I dont have any error and I dont know where my mistake is, could somebody please help me to solve this problem?
Thanks in advance.

Simple, set Allowsorting property true and add sorting event in your gridview.
<asp:GridView ID="GridView1" runat="server" AllowSorting="true"
OnSorting="GridView1_Sorting">
</asp:GridView>
Now add Event OnSorting in .cs file
protected void GridView1_Sorting(object sender, GridViewSortEventArgs e)
{
SetSortDirection(SortDireaction);
if (dataTable != null)
{
dataTable.DefaultView.Sort = e.SortExpression + " " +_sortDirection;
GridView1.DataSource = dataTable;
GridView1.DataBind();
SortDireaction = _sortDirection;
}
}
protected void SetSortDirection(string sortDirection)
{
if (sortDirection == "ASC")
{
_sortDirection = "DESC";
}
else
{
_sortDirection = "ASC";
}
}

I got the solution. Hope this will help others people that face this similar problem. On .aspx page need to change:
from OnSorting="ComponentGridView_Sorting"
to onsortcommand="ComponentGridView_Sorting"
Then put this code on aspx.cs(back-end code):
protected void Datagrid1_SortCommand(object source, DataGridSortCommandEventArgs e)
{
string strSQL;
DataTable dt;
strSQL = "YOUR SELECT STATEMENT (SQL)";
dt = strSQL;
{
string SortDir = string.Empty;
if (dir == SortDirection.Ascending)
{
dir = SortDirection.Descending;
SortDir = "Desc";
}
else
{
dir = SortDirection.Ascending;
SortDir = "Asc";
}
DataView sortedView = new DataView(dt);
sortedView.Sort = e.SortExpression + " " + SortDir;
Datagrid1.DataSource = sortedView;
Datagrid1.DataBind();
}
}
protected SortDirection dir
{
get
{
if (ViewState["dirState"] == null)
{
ViewState["dirState"] = SortDirection.Ascending;
}
return (SortDirection)ViewState["dirState"];
}
set
{
ViewState["dirState"] = value;
}
}

Do not take tension developers it's really too easy follow my steps
Step 1 Create GridView
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" AllowPaging="true" class="w3-table-all"
OnPageIndexChanging="OnPageIndexChanging" PageSize="20" >
<Columns>
<asp:BoundField HeaderStyle-CssClass="w3-blue" ItemStyle-CssClass="w3-hover-green" ItemStyle-Width="250px" DataField="sn_no" HeaderText="ID" />
<asp:BoundField HeaderStyle-CssClass="w3-blue" ItemStyle-CssClass="w3-hover-green" ItemStyle-Width="500px" DataField="name" HeaderText="Name" />
<asp:BoundField HeaderStyle-CssClass="w3-blue" ItemStyle-CssClass="w3-hover-green" ItemStyle-Width="500px" DataField="mo" HeaderText="Mobile" />
<asp:BoundField HeaderStyle-CssClass="w3-blue" ItemStyle-CssClass="w3-hover-green" ItemStyle-Width="500px" DataField="email" HeaderText="Email Id" />
<asp:BoundField HeaderStyle-CssClass="w3-blue" ItemStyle-CssClass="w3-hover-green" ItemStyle-Width="500px" DataField="loc" HeaderText="Location" />
<asp:BoundField HeaderStyle-CssClass="w3-blue" ItemStyle-CssClass="w3-hover-green" ItemStyle-Width="500px" DataField="date" HeaderText="Date" />
<asp:BoundField HeaderStyle-CssClass="w3-blue" ItemStyle-CssClass="w3-hover-green" ItemStyle-Width="500px" DataField="day2" HeaderText="Day" />
<asp:BoundField HeaderStyle-CssClass="w3-blue" ItemStyle-CssClass="w3-hover-green" ItemStyle-Width="500px" DataField="date" HeaderText="Date" />
<asp:BoundField HeaderStyle-CssClass="w3-blue" ItemStyle-CssClass="w3-hover-green" ItemStyle-Width="500px" DataField="time" HeaderText="Time" />
</Columns>
</asp:GridView>
Step 2 Goto *.aspx.cs file and write
a). For descending order
cmd = new MySqlCommand("SELECT * FROM appointment ORDER BY sn_no DESC", con);
b). For ascending order
cmd = new MySqlCommand("SELECT * FROM appointment ORDER BY sn_no ASC", con);
Thanks with love #Vaibhav Yadav
Vaibhav Designs
http://vaibhavdesigns.org
for more ...

<asp:GridView ID="GridView1" runat="server" AllowSorting="True" AutoGenerateColumns="False" CellPadding="4" DataKeyNames="empid" DataSourceID="SqlDataSource1" EnableModelValidation="True" ForeColor="#333333" GridLines="None">

Textbox In gridview not saving its value in table

I have a gridview gv_Products and a gridview Gv_selected. My products gridview has a checkbox that when is checked the selected row is entered in the gv_selected gridview.
I have added a textbox in gv_selected gridiew to enter the quantity i want to reorder. The quantity that i enter loses its value after i press the submit button.
<asp:GridView ID="gvSelected" runat="server"
AutoGenerateColumns = "False" Font-Names = "Arial" CssClass="gridviewsSmall" Font-Size = "11pt"
OnRowDataBound="GridView_gvSelected_RowDataBound" EnableViewState="False"
EmptyDataText = "No Records Selected" >
<Columns>
<asp:BoundField DataField="ProductId" HeaderText="Product ID" ReadOnly="True"
SortExpression="ProductId" />
<asp:TemplateField HeaderText="Product No" SortExpression="ProductNo">
<ItemTemplate>
<asp:Label ID="Label2" runat="server" Text='<%# Bind("ProductNo") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Product Name" SortExpression="Product_name">
<ItemTemplate>
<asp:Label ID="Label3" runat="server" Text='<%# Bind("Product_name") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="SupplierId" HeaderText="Supplier ID" ReadOnly="True"
SortExpression="SupplierId" />
<asp:TemplateField HeaderText="Quantity" SortExpression="Quantity">
<ItemTemplate>
<asp:TextBox ID="TextBox1" runat="server" Text='<%#Bind("Quantity") %>'></asp:TextBox>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
<asp:Button ID="btnSendOrder" Visible="false" runat="server" Text="Send Order"
onclick="btnSendOrder_Click" />
Here is my code behind for adding rows in gvSelected gridview
private DataTable CreateDataTable()
{
DataTable dt = new DataTable();
dt.Columns.Add("ProductId");
dt.Columns.Add("ProductNo");
dt.Columns.Add("Product_name");
dt.Columns.Add("SupplierId");
dt.Columns.Add("Quantity");
dt.AcceptChanges();
return dt;
}
private DataTable AddRow(GridViewRow gvRow, DataTable dt)
{
DataRow[] dr = dt.Select("ProductId = '" + gvRow.Cells[3].Text + "'");
if (dr.Length <= 0)
{
dt.Rows.Add();
dt.Rows[dt.Rows.Count - 1]["ProductId"] = gvRow.Cells[3].Text;
dt.Rows[dt.Rows.Count - 1]["ProductNo"] = (gvRow.FindControl("Label2") as Label).Text;
dt.Rows[dt.Rows.Count - 1]["Product_name"] = (gvRow.FindControl("Label3") as Label).Text;
dt.Rows[dt.Rows.Count - 1]["SupplierId"] = (gvRow.FindControl("Label5") as Label).Text;
dt.Rows[dt.Rows.Count - 1]["Quantity"] = 0;
dt.AcceptChanges();
}
return dt;
}
protected void CheckBox_CheckChanged(object sender, EventArgs e)
{
GetData();
SetData();
BindSecondaryGrid();
}
private void BindSecondaryGrid()
{
DataTable dt = (DataTable)ViewState["SelectedRecords"];
gvSelected.DataSource = dt;
gvSelected.DataBind();
}
And here is the submit button!
protected void btnSendOrder_Click(object sender, EventArgs e)
{
t_supplier_orders newOrder = new t_supplier_orders();
newOrder.UserName = User.Identity.Name;
newOrder.Order_date = DateTime.Now;
newOrder.Order_status = "Pending";
MembershipUser myObject = Membership.GetUser();
Guid UserID = new Guid(myObject.ProviderUserKey.ToString());
newOrder.UserId = UserID;
newOrder.SupplierId = Convert.ToInt32(ddl1.SelectedValue);
newOrder.Received_date = null;
Bohemian.t_supplier_orders.AddObject(newOrder);
Bohemian.SaveChanges();
//------------------------------------------------------------------------+
// Create a new OderDetail Record for each item in the gvSelected |
//------------------------------------------------------------------------+
foreach (GridViewRow row in gvSelected.Rows)
{
{
t_supplier_orders_details od = new t_supplier_orders_details();
TextBox txt1 = (TextBox)gvSelected.FindControl("TextBox1");
od.OrderId = newOrder.OrderId;
od.ProductId = Convert.ToInt32(row.Cells[0].Text);
od.Product_name = (row.FindControl("Label3") as Label).Text;
od.ProductNo = (row.FindControl("Label2") as Label).Text;
od.Quantity = Convert.ToInt32(txt1.text);
Bohemian.t_supplier_orders_details.AddObject(od);
}
}
Bohemian.SaveChanges();
lblSuccess.Text = "The Order has been successfully sent to supplier!!";
lblSuccess.ForeColor=System.Drawing.Color.BlueViolet;
lblSuccess.Font.Bold = true;
}

I assume that you are assigning the DataSource and DataBind the GridView on every postback. That will overwite all changes.
So wrap your code in a !IsPostBack check:
protected void Page_Load()
{
if(!IsPostBack)
{
BindSecondaryGrid();
}
}
By the way, you should not store the DataTable in ViewState since that will blow it up.

edit row in gridview

I would like to help me with my code. I have 2 gridviews. In the first gridview the user can choose with a checkbox every row he wants. These rows are transfered in the second gridview. All these my code does them well.Now, I want to edit the quantity column in second gridview to change the value but i don't know what i must write in edit box.
Here is my code:
using System;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Collections;
public partial class ShowLand : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
BindPrimaryGrid();
BindSecondaryGrid();
}
}
private void BindPrimaryGrid()
{
string constr = ConfigurationManager.ConnectionStrings["conString"].ConnectionString;
string query = "select * from Land";
SqlConnection con = new SqlConnection(constr);
SqlDataAdapter sda = new SqlDataAdapter(query, con);
DataTable dt = new DataTable();
sda.Fill(dt);
gridview2.DataSource = dt;
gridview2.DataBind();
}
private void GetData()
{
DataTable dt;
if (ViewState["SelectedRecords1"] != null)
dt = (DataTable)ViewState["SelectedRecords1"];
else
dt = CreateDataTable();
CheckBox chkAll = (CheckBox)gridview2.HeaderRow
.Cells[0].FindControl("chkAll");
for (int i = 0; i < gridview2.Rows.Count; i++)
{
if (chkAll.Checked)
{
dt = AddRow(gridview2.Rows[i], dt);
}
else
{
CheckBox chk = (CheckBox)gridview2.Rows[i]
.Cells[0].FindControl("chk");
if (chk.Checked)
{
dt = AddRow(gridview2.Rows[i], dt);
}
else
{
dt = RemoveRow(gridview2.Rows[i], dt);
}
}
}
ViewState["SelectedRecords1"] = dt;
}
private void SetData()
{
CheckBox chkAll = (CheckBox)gridview2.HeaderRow.Cells[0].FindControl("chkAll");
chkAll.Checked = true;
if (ViewState["SelectedRecords1"] != null)
{
DataTable dt = (DataTable)ViewState["SelectedRecords1"];
for (int i = 0; i < gridview2.Rows.Count; i++)
{
CheckBox chk = (CheckBox)gridview2.Rows[i].Cells[0].FindControl("chk");
if (chk != null)
{
DataRow[] dr = dt.Select("id = '" + gridview2.Rows[i].Cells[1].Text + "'");
chk.Checked = dr.Length > 0;
if (!chk.Checked)
{
chkAll.Checked = false;
}
}
}
}
}
private DataTable CreateDataTable()
{
DataTable dt = new DataTable();
dt.Columns.Add("id");
dt.Columns.Add("name");
dt.Columns.Add("price");
dt.Columns.Add("quantity");
dt.Columns.Add("total");
dt.AcceptChanges();
return dt;
}
private DataTable AddRow(GridViewRow gvRow, DataTable dt)
{
DataRow[] dr = dt.Select("id = '" + gvRow.Cells[1].Text + "'");
if (dr.Length <= 0)
{
dt.Rows.Add();
dt.Rows[dt.Rows.Count - 1]["id"] = gvRow.Cells[1].Text;
dt.Rows[dt.Rows.Count - 1]["name"] = gvRow.Cells[2].Text;
dt.Rows[dt.Rows.Count - 1]["price"] = gvRow.Cells[3].Text;
dt.Rows[dt.Rows.Count - 1]["quantity"] = gvRow.Cells[4].Text;
dt.Rows[dt.Rows.Count - 1]["total"] = gvRow.Cells[5].Text;
dt.AcceptChanges();
}
return dt;
}
private DataTable RemoveRow(GridViewRow gvRow, DataTable dt)
{
DataRow[] dr = dt.Select("id = '" + gvRow.Cells[1].Text + "'");
if (dr.Length > 0)
{
dt.Rows.Remove(dr[0]);
dt.AcceptChanges();
}
return dt;
}
protected void CheckBox_CheckChanged(object sender, EventArgs e)
{
GetData();
SetData();
BindSecondaryGrid();
}
private void BindSecondaryGrid()
{
DataTable dt = (DataTable)ViewState["SelectedRecords1"];
gridview3.DataSource = dt;
gridview3.DataBind();
}
}
and the source code is
<asp:GridView ID="gridview2" runat="server" AutoGenerateColumns="False"
DataKeyNames="id" DataSourceID="SqlDataSource5">
<Columns>
<asp:TemplateField>
<HeaderTemplate>
<asp:CheckBox ID="chkAll" runat="server" onclick = "checkAll(this);"
AutoPostBack = "true" OnCheckedChanged = "CheckBox_CheckChanged"/>
</HeaderTemplate>
<ItemTemplate>
<asp:CheckBox ID="chk" runat="server" onclick = "Check_Click(this)"
AutoPostBack = "true" OnCheckedChanged = "CheckBox_CheckChanged" />
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="id" HeaderText="id" InsertVisible="False"
ReadOnly="True" SortExpression="id" />
<asp:BoundField DataField="name" HeaderText="name"
SortExpression="name" />
<asp:BoundField DataField="price" HeaderText="price" SortExpression="price" />
<asp:BoundField DataField="quantity" HeaderText="quantity"
SortExpression="quantity" />
<asp:BoundField DataField="total" HeaderText="total" SortExpression="total" />
</Columns>
</asp:GridView>
<asp:SqlDataSource ID="SqlDataSource5" runat="server"
ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
SelectCommand="SELECT * FROM [Land]"></asp:SqlDataSource>
<br />
</div>
<div>
<asp:GridView ID="gridview3" runat="server"
AutoGenerateColumns = "False" DataKeyNames="id"
EmptyDataText = "No Records Selected" >
<Columns>
<asp:BoundField DataField = "id" HeaderText = "id" />
<asp:BoundField DataField = "name" HeaderText = "name" ReadOnly="True" />
<asp:BoundField DataField = "price" HeaderText = "price"
DataFormatString="{0:c}" ReadOnly="True" />
<asp:TemplateField HeaderText="quantity">
<EditItemTemplate>
<asp:TextBox ID="TextBox1" runat="server" Text='<%# Bind("quantity")%>'</asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label1" runat="server" Text='<%# Bind("quantity") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField = "total" HeaderText = "total"
DataFormatString="{0:c}" ReadOnly="True" />
<asp:CommandField ShowEditButton="True" />
</Columns>
</asp:GridView>
<asp:Label ID="totalLabel" runat="server"></asp:Label>
<br />
</div>
</form>
</body>
</html>

This is not particular asp.net solution but that's how I do something like this in my Windows app.
First of all you shoul make shure that there's a selected row in your GridView (gridView.SelectedRow != null). DataTable object allows you to get access to desired row by accessing it not by numeric index but by DataRow-type object index. After getting a reference to the row which fields' value you want to modify just go ahead with changes.
Here's the example:
if (gridView.SelectedRow != null)
{
dataTable.Rows[gridView.SelectedRow].BeginEdit();
dataTable.Rows[gridView.SelectedRow]["yourFieldName"] = newValue;
dataTable.Rows[gridView.SelectedRow].EndEdit();
gridView.DataSource = dataTable;
}
Hope my answer is of any help because I've never dealt with asp.net before.