Dynamically adding Textbox in asp.net using C# - asp.net

Question

I have written a code in which a textbox is dynamically added to a gridview cell. There is some default texts in the textbox. I want that when users will click on the textbox the default text will disappear and the user can then write anything on it only in number, i.e. the user will not be able to use letters or special characters.
Kindly let me know how to achieve this.
Code example
Gridview gv=new Gridview();
gv.DataSource=dt;
gv.DataBind();
Textbox t1 = new Textbox();
t1.Text="Outages if any(in mins)";
gv.Rows[0].Cells[0].Controls.Add(t1);
Need help after this, something like when user puts his cursor in the textbox , the default text will disappear , and if the user removes the cursor without writing anything , the default text will reappear. Also the default text should be a bit blurred
Thanks.

Answer 1

Try something like this
Textbox t1 = new Textbox();
t1.Attributes.Add("onclick", "if(this.value == 'default text') this.value = '';"
t1.Attributes.Add("onblur", "if(this.value == '') this.value = 'default text';" />
You could also use onfocus in case users use tab key
With this, using this.value, approach you don't need to know the client ID of the control.

Answer 2

Here is a post describing exactly what you are looking to do:
HowTo: including default text in a Textbox while enforcing server-side validation
The pertinent points are:
Adding javascript attribute to onfocus & and onblur:
txtName.Attributes.Add("onfocus","clearText()");
txtName.Attributes.Add("onblur","resetText()");
Adding the javascript to clear and repopulate the textbox:
function clearText() {
document.form1.txtName.value = ""
}
function resetText() {
if(document.form1.txtName.value == "")
document.form1.txtName.value = "(enter something here)"

Answer 3

You can do this. The easiest way is to use the ajaxControlToolkit. You can create controls dynamically. For example:
Dim mt As new TextBox
Dim newTest As New AjaxControlToolkit.TextBoxWatermarkExtender
With mt
.ID = "textBox1"
.TextMode = TextBoxMode.SingleLine
End With
With newTest
.ID = "TextBoxWatermarkExtender1"
.TargetControlID = mt.ClientID
.WatermarkText = "test"
End With
Then just add both controls to the gridview as you are doing with the textbox. If you are not using Ajax, you can add javascript to the control through codebehind but this is more difficult. Let me know if that is what you want to do and Ill add some code to show you how.
This should create a textbox control with an associated ajax TextBoxWaterMarkExtender.