i am using a DataList that contains a few TextBox within a table. i had tried the code is the code behind
TextBox txtbox = dlCRR.FindControl("TextBox1") as TextBox;
The error is
Object reference not set to an instance of an object.
When i debug i am seeing a null value. why is this?
You won't be able to find the textbox directly from the datalist control. You will have to find it from the DataList.Items.
Ex:
TextBox txt = myDataList.Items[indexOfWhatIamLookingFor].FindControl("TextBox1") as TextBox;
or if you want to iterate all items
foreach (DataListItem dli in myDataList.Items)
{
TextBox txt = dli.FindControl("TextBox1") as TextBox;
}
Related
in asp.net TextBox will create pressure to button1's. Button2 to the pressure inside the TextBox data consisting of label1 my yazdırıca. I tried to do it like this gives an error.
Object reference not set to an instance of an object.
button1_click{
TextBox txt = new TextBox();
txt.ID = "a";
txt.EnableViewState = true;
Panel1.Controls.Add(txt);
}
Button2_click{
TextBox deneme= Panel1.FindControl("a") as TextBox;
Label1.Text = deneme.Text;
}
After you create your control, on the first click, the control shown on the page and exist.
On the second click the page is not know any more about that text control because you did not save that information somewhere and because only you know that some time in the past you create it.
So on this code you have:
Button2_click{
TextBox deneme= Panel1.FindControl("a") as TextBox;
// here the deneme is null ! and you get the exception !
// the deneme is not exist on the second click, not saved anywhere
Label1.Text = deneme.Text;
}
The solution is to keep on viewstate what control you create and how, and re-create them on PageInit. Alternative you can redesign your page and think a different approach to that, eg you can have the TextControl's all ready on page hidden, and just open them.
Button2_click{
TextBox txt = (TextBox)Panel1.FindControl("a");
Label Label1 = new Label();
Label1.Text=txt.Texxt;
}
I am building many textboxes programmatically in my ASP.NET page, after I've clicked a button, I would like to process those values, is there any possibility to retrieve them from their ID in ViewState ?
Here is my code :
Reference of the table in the aspx :
<asp:Table ID="Distances" runat="server" ViewStateMode="Inherit"></asp:Table>
Then in code behind after creating all the rows and cells, I add a textbox into some of them :
Distances.Rows[j].Cells[i].Controls.Add(CreateTB(distance.ToString(), (i + j * rows).ToString(), false));
protected TextBox CreateTB(string text, string id, bool ebanled = true)
{
TextBox tb = new TextBox() { Text = text, ID = id, Enabled = ebanled};
tb.TextChanged += new EventHandler(OnTBChanged);
return tb;
}
ViewState is enabled by default, so it should already work that the Text property is persisted across postbacks.
So you could for example use FindControl("TextBoxID") or enumerate them to get the refernce to the TextBox (assuming that they are added to a container-control like Panel):
foreach(TextBox txt in MyPanel.Controls.OfType<TextBox>())
{
String text = txt.Text;
}
or
TextBox txt = (TextBox)MyPanel.FindControl("TextBox1")
String text = txt.Text;
I assume you're not recreating those TextBoxes on postbacks. Therefore you need to use the same ID as before and recreate them in Page_Load at the latest stage in page's life-cycle. So you can create them in an event, but you cannot recreate them there.
You should show your code where you create them dynamically, then i could be more specific.
TRULY UNDERSTANDING DYNAMIC CONTROLS
I am using C# ASP.net, and relative new to it, and need to accomplish below.
In my VS2010 web application project I have webform with a Gridview which fetches the data from a table.
In the Grid, I have Commandfiled Button (column1) and Item template with Dropdownlist (column2).
Use case is, user first selects one listitem from 3 list items (H, L and M) and then selects command button.
I am not able to figure out how to extract selected listitem from a selected row
protected void GridView2_SelectedIndexChanged(object sender, EventArgs e)
{
GridViewRow row = GridView2.SelectedRow;
Label4.Text = "You selected " + row.Cells[4].Text + ".";
Label5.Text = "You selected this list item from dropdownlist " + ???? ;
}
Thanks in advance.
The GridViewRow object provides the method FindControl (as do all container controls) to get access to a control in the row by its id. For example, if your DropDownList has an id of MyDropDown, you could use the following to access its selected value:
GridViewRow row = GridView2.SelectedRow;
DropDownList MyDropDown = row.FindControl("MyDropDown") as DropDownList;
string theValue = MyDropDown.SelectedValue;
// now do something with theValue
This is the recommended method for accessing all controls in your GridView. You want to avoid doing things like row.Cells[#] as much as possible, because it easily breaks when you re-arrange or add/remove columns from your GridView.
My problem is:
I have a GridView, which is bound to list of declared DTO objects with column of CheckBoxes. Also, I have a "Save" button on the page. My mission concludes in getting all rows, where CheckBox is checked and get the containing data. Unfortunately, row.DataItem = null on Button1_Click, because, I'm using if(!IsPostBack) gw.DataBind() statement (otherwise, I can't get CheckBox status). Could you give me the best practice for solving my problem?
Thank you in advance!
If you do if(!IsPostBack) --> gw.DataBind(), that will reinitialize your GridView and the checkboxes will be set to unchecked again.
In your case, in Button1_Click event, you can loop through each DataRow on your GridView and find the row which has it's checkbox checked and get all the selected row data.
foreach (GridViewRow gvRow in gw.Rows) {
// Find your checkbox
CheckBox chkBox = (CheckBox)gvRow.FindControl("checkBox");
if (chkBox.Checked) {
// Get your values
string value1 = gvRow.Cells[1].Text;
string value2 = gvRow.Cells[2].Text;
// etc...
}
}
I have done a project in ASP.Net that asks to input a number in textbox. After typing a number in it and click a button it generates the number of textbox according to the value given in the textbox. Like if I type 5 in the textbox it dynamically generates 5 textboxes below.
I want all the value of dynamically created textbox(more than one textbox) to be stored in session and pass to next page through session after clicking another button. But i could not do that.
How can i solve this problem.
Anyone can help me.
Thanks
You could create an array with the values and store that in the session. Code below is untested, but should give you an idea.
string[] arrayTextboxes = new string[numberOfTextboxes];
int index = 0;
foreach (Control ctrl in Page.Controls)
{
if (ctrl is TextBox)
{
arrayTextboxes[index] = ((Textbox)ctrl).Text;
index++;
}
}
Session["tbValues"] = arrayTextboxes;