Determines whether multiple textbox items are empty.

1. Judgment of the entire page

Foreach (control CTL in this. controls [1]. Controls)
{
If (CTL. GetType (). Name = "textbox ")
{
Textbox TB = new Textbox ();
TB = (textbox) This. findcontrol (CTL. ID );

If (Tb. Text = string. Empty)
{
The value of response. Write ("<SCRIPT> alert ('" + CTL. ID + "is null. '); </SCRIPT> ");
Break;
}
}
}

2. Specify textbox judgment in formid

First find your form ID
Protected htmlform yourformid;

Foreach (Object OBJ in yourformid. Controls)
{
If (obj is textbox)
{
Textbox TB = (textbox) OBJ;
If (Tb. Text = string. Empty)
{
The value of response. Write ("<SCRIPT> alert ('" + Tb. ID + "is null. '); </SCRIPT> ;")
}
}
}