Develop Reference

Adding a dropdown list from server side

i have this following code :
<asp:DropDownList ID="dd_SubCategory" Width="160px" runat="server" DataTextField="CATEGORY_NAME" DataValueField="CATEGORY_ID"></asp:DropDownList>
<br />
<asp:Panel ID="pnl_SubCatg" runat="server"></asp:Panel>
<asp:ImageButton ID="Ib_AddSubCategory" runat="server" OnClick="Ib_AddSubCategory_Click" ImageUrl="/images/add.gif" />
protected void Ib_AddSubCategory_Click(object sender, ImageClickEventArgs e)
{
string SelectedCategory="";
if (ctrl_list.Count == 0)
SelectedCategory = dd_SubCategory.SelectedValue;
else
SelectedCategory = Session["Selected_SubCatg"] != null && Session["Selected_SubCatg"].ToString()!=""?Session["Selected_SubCatg"].ToString():((DropDownList)ctrl_list[ctrl_list.Count - 1]).SelectedValue;
try
{
DataRow[] Rows = DataHelper.TicketCategories.Select("PARENT_CATEGORY_ID='" + SelectedCategory + "'");
if (Rows.Length > 0)
{
AddSubCategory(Rows);
}
foreach (Control item in ctrl_list)
pnl_SubCatg.Controls.Add(item);
}
catch (Exception ex)
{ }
}
List<Control> _ctrl_list = null;
List<Control> ctrl_list {
get
{
if (Session["SUB_CATG_LIST"] == null)
{
_ctrl_list = new List<Control>();
Session["SUB_CATG_LIST"] = _ctrl_list;
}
return Session["SUB_CATG_LIST"] as List<Control>;
}
}
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
Session["SUB_CATG_LIST"] = null;
Session["Selected_SubCatg"] = null;
}
if (ctrl_list.Count > 0)
{
foreach (Control item in ctrl_list)
pnl_SubCatg.Controls.Add(item);
}
}
private void AddSubCategory(DataRow [] Rows)
{
DropDownList dd_SubCategory1 = new DropDownList();
dd_SubCategory1.Width = Unit.Pixel(160);
dd_SubCategory1.DataTextField = "CATEGORY_NAME";
dd_SubCategory1.DataValueField = "CATEGORY_ID";
dd_SubCategory1.ID = Guid.NewGuid().ToString();
dd_SubCategory1.DataSource = Rows.CopyToDataTable();
dd_SubCategory1.DataBind();
dd_SubCategory1.SelectedIndexChanged += dd_SubCategory1_SelectedIndexChanged;
dd_SubCategory1.AutoPostBack = true;
ctrl_list.Add(dd_SubCategory1);
}
void dd_SubCategory1_SelectedIndexChanged(object sender, EventArgs e)
{
Session["Selected_SubCatg"] = ((DropDownList)sender).SelectedValue;
}
i am trying to add a dropdown list containing the subcategories of the last inserted dropdown list , my problem is dd_SubCategory1_SelectedIndexChanged is not firing and i can't get the and the selectedValue of the last dropdownlist is always the same

That is because its dynamically generated and it will lose its state after its rendered on your page.
To access the dropdown and its related events and properties, you will need to recreate it everytime your page is postback.
Hope its clear enough.

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);
}
}

Using PostBackUrl, Getting PreviousPage.Control()

I'm using PostBackUrl to post my control from a "firstwebpage.aspx" to a "secondwebpage.aspx" so that I would be able to generate some configuration files.
I do understand that I can make use of PreviousPage.FindControl("myControlId") method in my secondwebpage.aspx to get my control from "firstwebpage.aspx"and hence grab my data and it worked.
However, it seems that this method does not work on controls which I generated programmically during runtime while populating them in a table in my firstwebpage.aspx.
I also tried using this function Response.Write("--" + Request["TextBox1"].ToString() + "--");
And although this statement do printout the text in the textfield on TextBox1, it only return me the string value of textbox1. I am unable to cast it to a textbox control in the following format too
TextBox temptextBox = (TextBox)Request["TextBox1"];
My question is, how can I actually access the control which i generated programmically in "firstwebpage.aspx" on "secondwebpage.aspx"?
Please advice!
thanks alot!
//my panel and button in aspx
<asp:Panel ID="Panel2" runat="server"></asp:Panel>
<asp:Button ID="Button1" runat="server" Text="Generate Xml" PostBackUrl="~/WebForm2.aspx" onclick="Button1_Click" />
//this is my function to insert a line into the panel
public void createfilerow(string b, string path, bool x86check, bool x86enable, bool x64check, bool x64enable)
{
Label blank4 = new Label();
blank4.ID = "blank4";
blank4.Text = "";
Panel2.Controls.Add(blank4);
CheckBox c = new CheckBox();
c.Text = b.Replace(path, "");
c.Checked = true;
c.ID = "1a";
Panel2.Controls.Add(c);
CheckBox d = new CheckBox();
d.Checked = x86check;
d.Enabled = x86enable;
d.ID = "1b";
Panel2.Controls.Add(d);
CheckBox e = new CheckBox();
e.Checked = x64check;
e.Enabled = x64enable;
e.ID = "1c";
Panel2.Controls.Add(e);
}
//my virtual path in WebForm2.aspx
<%# PreviousPageType VirtualPath="~/WebForm1.aspx" %>
//my pageload handler
protected void Page_Load(object sender, EventArgs e)
{
if (PreviousPage != null)
{
CheckBox tempCheckbox = (CheckBox)Page.PreviousPage.FindControl("1a");
Button1.Text = tempCheckbox.Text;
}
}
//handler which will populate the panel upon clicking
protected void Button7_Click(object sender, EventArgs e)
{
//get foldername
if (!Directory.Exists(#"myfilepath" + TextBox2.Text))
{
//folder does not exist
//do required actions
return;
}
string[] x86files = null;
string[] x64files = null;
string[] x86filespath = null;
string[] x64filespath = null;
ArrayList common = new ArrayList();
if (Directory.Exists(#"myfilepath" + TextBox2.Text + "\\x86"))
x86files = Directory.GetFileSystemEntries("myfilepath" + TextBox2.Text + "\\x86");
if (Directory.Exists(#"myfilepath" + TextBox2.Text + "\\x64"))
x64files = Directory.GetFileSystemEntries("myfilepath" + TextBox2.Text + "\\x64");
//some codes to convert x64files and x86files to string[]
//The header for Panel, 4 column
Label FL = new Label();
FL.ID = "flavourid";
FL.Text = "Flavour";
Panel2.Controls.Add(FL);
Label filetext = new Label();
filetext.ID = "filenamelabel";
filetext.Text = "File(s)";
Panel2.Controls.Add(filetext);
Label label86 = new Label();
label86.ID = "label86";
label86.Text = "x86";
Panel2.Controls.Add(label86);
Label label64 = new Label();
label64.ID = "label64";
label64.Text = "x64";
Panel2.Controls.Add(label64);
//a for loop determine number of times codes have to be run
for (int a = 0; a < num; a++)
{
ArrayList location = new ArrayList();
if (//this iteration had to be run)
{
string path = null;
switch (//id of this iteration)
{
case id:
path = some network address
}
//check the current version of iternation
string version = //version type;
//get the platform of the version
string platform = //platform
if (curent version = certain type)
{
//do what is required.
//build a list
}
else
{
//normal routine
//do what is required
//build a list
}
//populating the panel with data from list
createflavourheader(a);
//create dynamic checkboxes according to the list
foreach(string s in list)
//createrow parameter is by version type and platform
createfilerow(readin, path, true, true, false, false);
}
}
}
form1.Controls.Add(Panel2);
}
Sorry can't show you the full code as it is long and I believe it should be confidential even though i wrote them all

Yes you can access, Below is an example
// On Page1.aspx I have a button for postback
<asp:Button ID="btnSubmit" runat="server" Text="Submit"
PostBackUrl="~/Page2.aspx" />
// Page1.aspx.cs
protected void Page_Load(object sender, EventArgs e)
{
TextBox t = new TextBox(); // created a TextBox
t.ID = "myTextBox"; // assigned an ID
form1.Controls.Add(t); // Add to form
}
Now on the second page I will get the value of TextBox as
// Page2.aspx.cs
protected void Page_Load(object sender, EventArgs e)
{
if (PreviousPage != null)
{
TextBox t = (TextBox) PreviousPage.FindControl("myTextBox");
string mytboxvalue = t.Text;
}
// OR
string myTextBoxValue = Request.Form["myTextBox"];
}
Updated Answer:
Panel myPanel = new Panel();
myPanel.ID = "myPanel";
TextBox t = new TextBox();
t.ID = "myTextBox";
myPanel.Controls.Add(t);
TextBox t1 = new TextBox();
t1.ID = "myTextBox1";
myPanel.Controls.Add(t1);
// Add all your child controls to your panel and at the end add your panel to your form
form1.Controls.Add(myPanel);
// on the processing page you can get the values as
protected void Page_Load(object sender, EventArgs e)
{
if (PreviousPage != null)
{
TextBox t = (TextBox) PreviousPage.FindControl("myTextBox");
string mytboxvalue = t.Text;
}
string myTextBoxValue = Request.Form["myTextBox1"];
}

I also tried using this function Response.Write("--" +
Request["TextBox1"].ToString() + "--"); And although this statement do
printout the text in the textfield on TextBox1, it only return me the
string value of textbox1. I am unable to cast it to a textbox control
in the following format too
TextBox temptextBox = (TextBox)Request["TextBox1"];
Hi lw,
I think you may try passing the type of control (e.g. 'tb') together with the content and creating a new object (e.g. TextBox) and assign it to templtexBox object.
My 20 cents.
Andy