Develop Reference

Not able to access dynamically generated templated field controls

I am creating dynamic Template Fields for my gridview:
<asp:GridView ID="grdData" runat="server" DataKeyNames = "ID" AutoGenerateColumns="false" OnRowDataBound="grdData_RowDataBound">
<Columns>
<asp:TemplateField>
<HeaderTemplate>
<asp:CheckBox ID="chkAll" AutoPostBack="true" OnCheckedChanged="OnCheckedChanged" runat="server" />
</HeaderTemplate>
<ItemTemplate>
<asp:CheckBox ID="editbtn" AutoPostBack="true" OnCheckedChanged="OnCheckedChanged" runat="server" />
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
the code to add templateField is below:
private void BindGridView(DataTable dtData)
{
foreach (DataColumn item in dtData.Columns)
{
TemplateField tfield = new TemplateField();
tfield.HeaderText = item.ToString();
grdData.Columns.Add(tfield);
}
grdData.DataSource = dtData;
ViewState["dtDataTable"] = dtData;
grdData.DataBind();
}
and in row databound I am adding textbox and label to the templatefield:
protected void grdData_RowDataBound(object sender, GridViewRowEventArgs e)
{
DataTable dtData = (DataTable)ViewState["dtDataTable"];
if (e.Row.RowType == DataControlRowType.DataRow)
{
int i = 1;
foreach (DataColumn item in dtData.Columns )
{
TextBox txtBox = new TextBox();
txtBox.ID = "txt"+item.ToString();
txtBox.Text = (e.Row.DataItem as DataRowView).Row[item.ToString()].ToString();
txtBox.Visible = false;
e.Row.Cells[i].Controls.Add(txtBox);
Label lblBox = new Label();
lblBox.ID = "lbl" + item.ToString();
lblBox.Text = (e.Row.DataItem as DataRowView).Row[item.ToString()].ToString();
e.Row.Cells[i].Controls.Add(lblBox);
i++;
}
}
}
Everything is working good so far,The grid is getting created and the values are getting populated ,but when i am calling below method and try to access the gridview control ,its throwing object reference error:
protected void OnCheckedChanged(object sender, EventArgs e)
{
bool isUpdateVisible = false;
CheckBox chk = (sender as CheckBox);
if (chk.ID == "chkAll")
{
foreach (GridViewRow row in grdData.Rows)
{
if (row.RowType == DataControlRowType.DataRow)
{
row.Cells[0].Controls.OfType<CheckBox>().FirstOrDefault().Checked = chk.Checked;
}
}
}
CheckBox chkAll = (grdData.HeaderRow.FindControl("chkAll") as CheckBox);
chkAll.Checked = true;
foreach (GridViewRow row in grdData.Rows)
{
if (row.RowType == DataControlRowType.DataRow)
{
bool isChecked = row.Cells[0].Controls.OfType<CheckBox>().FirstOrDefault().Checked;
for (int i = 1; i < row.Cells.Count; i++)
{
Label test= row.FindControl("lblName") as Label;//this is coming null
Below code lines are throwing object reference error as they are not able to find control
row.Cells[i].Controls.OfType<Label>().FirstOrDefault().Visible = !isChecked;//this line throwing object reference error
if (row.Cells[i].Controls.OfType<TextBox>().ToList().Count > 0)
{
row.Cells[i].Controls.OfType<TextBox>().FirstOrDefault().Visible = isChecked;
}
if (row.Cells[i].Controls.OfType<DropDownList>().ToList().Count > 0)
{
row.Cells[i].Controls.OfType<DropDownList>().FirstOrDefault().Visible = isChecked;
}
if (isChecked && !isUpdateVisible)
{
isUpdateVisible = true;
}
if (!isChecked)
{
chkAll.Checked = false;
}
}
}
}
btnUpdate.Visible = isUpdateVisible;
}
Edit:
I tried reinistialising the controls in preinit event but still no luck:
protected void Page_PreInit(object sender, EventArgs e)
{
if (ViewState["gridData"] != null)
{
BindGridView((DataTable)ViewState["gridData"]);
}
}
What I am doing wrong?

I recreated the dynamic gridview Controls in OnRowCreated as this event gets called in every postback instead of onRowDataBound Event and it worked like charm.

Integer only validation for dynamically added Textbox inside Asp.net Gridview

Below is how my GridView code , since the datatable is a pivoted value so the number of columns cannot be predicted. So I am adding textbox dynamically through code.
<asp:GridView ID="gvData"
EmptyDataText="There are no data records to display."
runat="server" AutoGenerateColumns="false"
HeaderStyle-BackColor="#3AC0F2"
HeaderStyle-ForeColor="White" OnRowDataBound="gvData_RowDataBound" >
<RowStyle BorderColor="LightBlue" />
</asp:GridView>
protected void Page_Load(object sender, EventArgs e)
{
foreach (var item in columnNames)
{
TemplateField tfield = new TemplateField();
tfield.HeaderText = item;
gvData.Columns.Add(tfield);
}
gvData.DataSource = ds.Tables[0];
gvData.DataBind();}
protected void gvData_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
for (int i = 3; i < columnNames.Length; i++)
{
TextboxCount++;
TextBox txtName = new TextBox();
txtName.ID = "txt" + Convert.ToString(TextboxCount);
txtName.BorderStyle = BorderStyle.None;
txtName.Text = (e.Row.DataItem as DataRowView).Row[columnNames[i]].ToString();
e.Row.Cells[i].Controls.Add(txtName); }}}
Now when user try to change value in the textbox I have to validate that they only enter integer value.
Here I am not sure what has to be done.

You can use int.TyrParse method
Example
int number;
string s = "AA";
bool IsInteger = int.TryParse(s, out number);

You could use javascript function and that to textbox from code behind like:
// Add this gvData_RowDataBound , allownumbers is a javascript function
txtName.Attributes.Add("onkeypress", "javascript:return allownumbers(event);");
Or else if you are using .NET 4.5 version then try out this:
txtName.Attributes["type"] = "number";

Grab user input from dynamic text box

I have two buttons. One button that creates the Textbox and another that submits the information. I'm having trouble retrieving the users texts once the textbox has been created. Here is the code:
private void CreateTextBox(int j) //Creates the fields / cells
{
TextBox t = new TextBox();
t.ID = "Textbox" + j;
//t.Text = "Textbox" + j;
lstTextBox.Add(t);
var c = new TableCell();
c.Controls.Add(t);
r.Cells.Add(c);
table1.Rows.Add(r);
Session["test"] = lstTextBox;
}
protected void Button2_Click(object sender, EventArgs e)
{
string[] holder = new string[4];
for (int i = 0; i < holder.Length; i++)
{
holder[i] = "";
}
List<TextBox> lstTextBox = (Session["test"] as List<TextBox>);
if (lstTextBox.Count < Counter)
{
int i = lstTextBox.Count;
for (int j = 0; j < i; j++)
{
holder[j] = lstTextBox[j].Text;
}
SqlConnection conns = new SqlConnection(ConfigurationManager.ConnectionStrings["TestDBConnectionString1"].ConnectionString);
SqlCommand cmd = new SqlCommand("Insert into LoanerForm (field0, field1, field2, field3) Values (#field0, #field1, #field2, #field3)", conns);
cmd.CommandType = CommandType.Text;
cmd.Parameters.AddWithValue("#field0", holder[0]);
cmd.Parameters.AddWithValue("#field1", holder[1]);
cmd.Parameters.AddWithValue("#field2", holder[2]);
cmd.Parameters.AddWithValue("#field3", holder[3]);
conns.Open();
cmd.ExecuteNonQuery();
conns.Close();
}
Counter = 0;
Button1.Visible = true; //Going to submit data to SQL
}
Thank you in advance!

Here is how you create TextBoxes dynamically. It keeps track of the number of textboxes in ViewState.
<asp:Button runat="server" ID="Button1" OnClick="Button1_Click"
Text="Create TextBoxes" />
<asp:Button runat="server" ID="Button2" OnClick="Button2_Click"
Text="Save TextBoxes to Database" />
<asp:PlaceHolder runat="server" ID="PlaceHolder1"></asp:PlaceHolder>
public int Counter
{
get { return Convert.ToInt32(ViewState["Counter"] ?? "0"); }
set { ViewState["Counter"] = value; }
}
protected void Page_Load(object sender, EventArgs e)
{
// Need to reload those textboxes on page back
// Otherwise, they will becomes null
int total = Counter;
for (int i = 0; i < total; i++)
{
var textBox = new TextBox
{
ID = "TextBox" + i,
Text = "TextBox" + i
};
PlaceHolder1.Controls.Add(textBox);
}
}
private void CreateTextBox(int id)
{
var textBox = new TextBox
{
ID = "TextBox" + id,
Text = "TextBox" + id
};
PlaceHolder1.Controls.Add(textBox);
}
protected void Button1_Click(object sender, EventArgs e)
{
CreateTextBox(Counter);
Counter = Counter + 1;
}
protected void Button2_Click(object sender, EventArgs e)
{
int total = Counter;
for (int i = 0; i < total; i++)
{
var textbox = PlaceHolder1.FindControl("TextBox" + i) as TextBox;
var text = textbox.Text;
// Do something with text
}
}

Don't store the TextBoxes in Session; rather, create them on the page.
The trick is creating them at the right time EVERY time (i.e. with each PostBack). Try loading them OnLoad() for the page (or CreateChildControls() if possible).
Once you do that, ASP.NET will automatically associate the input with the TextBox and you should be able to reference them as you normally would or via .FindControl() of the parent.

I think You used big program for generating dynamic textboxes and inserting into data base.For retriving text from dynamically generated textboxes,use the code below..
Request.Form["Textbox" + i.ToString()]
where "i" represents the number of textboxes you generated.
For more info.Please Check the below link.
how to insert value to sql db from dynamically generated textboxes asp.net

ASP Text box ID assignment using a for loop.?

I am a noob and i've been trying to figure out how we may assign an ID to asp:TextBox tags on creation in ASP.NET using c#.
Example:
I need to create a thread that may have multiple textboxes.
When a user clicks on a button, a text box must be generated with an ID say, txt01. On being clicked the second time, the ID of the generated text box must be txt02 and so on..depending on the number of clicks.
Thanks in Advance.

Remember last ID in some variable, for example int lastID, then in button's onClick method when creating the new TextBox assign its ID="txt"+lastID;.
You have to persist the lastID during page postbacks, you can store it in a ViewState.

Take and placeholder in your aspx page: eg: <asp:PlaceHolder runat="server" ID="pholder" />
and in code behind:
TextBox txtMyText = new TextBox();
tb1.ID = YourDynamicId;
pholder.Controls.Add(txtMyText);
You can save current id in ViewState and get the same id and assign incremented id to your dynamic textbox.

Try This:
int i = 1;
if (ViewState["i"] == null)
{
ViewState["i"] = i;
}
else
i = (int)ViewState["i"];
PlaceHolder1.Controls.Clear();
for (int j = 1; j <= i; j++)
{
TextBox TextBox = new TextBox();
TextBox.ID = "TextBox" + j.ToString();
PlaceHolder1.Controls.Add(TextBox);
}
ViewState["i"] = i + 1;
add this on your .aspx page
<asp:PlaceHolder ID="PlaceHolder1" runat="server"></asp:PlaceHolder>
Hope This help.

I think this is what you are looking for -
You will notice that I have used Page_Init because if you create/add the controls in Page_Load then FindControl will return null in PostBack. And also any data you entered in the dynamically added controls will not persist during Postbacks.
But Page_Init is called before ViewState or PostBack data is loaded. Therefore, you can not use ViewState or any other controls to keep the control count. So I have used Session to keep the count.
Try it out and let me know what you think.
ASPX Page
<form id="form1" runat="server">
<asp:PlaceHolder ID="PlaceHolder1" runat="server"></asp:PlaceHolder>
<asp:Button ID="btnCreate" runat="server" Text="Create" OnClick="btnCreate_Click" />
<asp:Button ID="btnRead" runat="server" Text="Read" OnClick="btnRead_Click" />
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
</form>
Code Behind
protected int NumberOfControls
{
get { return Convert.ToInt32(Session["noCon"]); }
set { Session["noCon"] = value.ToString(); }
}
private void Page_Init(object sender, System.EventArgs e)
{
if (!Page.IsPostBack)
//Initiate the counter of dynamically added controls
this.NumberOfControls = 0;
else
//Controls must be repeatedly be created on postback
this.createControls();
}
private void Page_Load(object sender, System.EventArgs e)
{
}
protected void btnCreate_Click(object sender, EventArgs e)
{
TextBox tbx = new TextBox();
tbx.ID = "txtData"+NumberOfControls;
NumberOfControls++;
PlaceHolder1.Controls.Add(tbx);
}
protected void btnRead_Click(object sender, EventArgs e)
{
int count = this.NumberOfControls;
for (int i = 0; i < count; i++)
{
TextBox tx = (TextBox)PlaceHolder1.FindControl("txtData" + i.ToString());
//Add the Controls to the container of your choice
Label1.Text += tx.Text + ",";
}
}
private void createControls()
{
int count = this.NumberOfControls;
for (int i = 0; i < count; i++)
{
TextBox tx = new TextBox();
tx.ID = "txtData" + i.ToString();
//Add the Controls to the container of your choice
PlaceHolder1.Controls.Add(tx);
}
}

store the id in a ViewState something like this
First initialise a count variable similiar to this.
in your class write this
protected int replyCount //declare the variable
{
get { return (int)ViewState["replyCount"]; }
set { ViewState["replyCount"] = value; }
}
In your page Load write this to initialise the replyCount if its not a postback;
protected void Page_Load(object sender, EventArgs e)
{
if(!page.IsPostBack)
{
replyCount = 0; //initialise the variable
}
}
then while creating dynamic textboxes
protected void Button_Click(Object sender, EventArgs e)
{
TextBox tb = new TextBox();
tb.id = "tb" + replycount; //use the variable
replycount++; // and after using increment it.
form.controls.add(tb); // assuming your form name is "form"
}
Thats it you should do.

Get new dropdownlist boxes On button click in asp.net c# with different Ids and assign datasource, along with selection changed functionality

I need to generate 3 DropDownList Boxes in a row Dynamically on ADD Button click event. Once the DDL is generated i should be able to assign Data source to it and also do DDL-selectedEventChanged functionality on them in c# asp.net.
Below link was exactly am looking for but i couldn't assign data source or i couldn't do any functionality
"Adding multiple DropDownLists with a button click"
any better Ideas please help
if i press Button i need to get 3 DDLs at a time, if i press again it should generate again, so number of clicks= no. of rows with three DDL's in each row

Here is the sample code. The only trick is that you need to load those dynamic controls again after post back. Otherwise, you won't be able to access those.
<asp:PlaceHolder runat="server" ID="PlaceHolder1"></asp:PlaceHolder>
<asp:Button runat="server" ID="AddButton" OnClick="AddButton_Click" Text="Add" />
private List<int> _controlIds;
private List<int> ControlIds
{
get
{
if (_controlIds == null)
{
if (ViewState["ControlIds"] != null)
_controlIds = (List<int>)ViewState["ControlIds"];
else
_controlIds = new List<int>();
}
return _controlIds;
}
set { ViewState["ControlIds"] = value; }
}
private List<string> DataSource
{
get { return new List<string> { "One", "Two", "Three" }; }
}
protected void Page_Load(object sender, EventArgs e)
{
if (IsPostBack)
{
var dataSource = DataSource;
foreach (int id in ControlIds)
{
var ddl = new DropDownList();
ddl.ID = id.ToString();
foreach (var data in dataSource)
ddl.Items.Add(new ListItem(data));
PlaceHolder1.Controls.Add(ddl);
}
}
}
protected void AddButton_Click(object sender, EventArgs e)
{
var dataSource = DataSource;
for (int i = 0; i < 3; i++)
{
var reqs = ControlIds;
int id = ControlIds.Count + 1;
reqs.Add(id);
ControlIds = reqs;
var ddl = new DropDownList();
ddl.ID = id.ToString();
foreach (var data in dataSource)
ddl.Items.Add(new ListItem(data));
PlaceHolder1.Controls.Add(ddl);
}
}