While writing code for connecting two webparts,I created a two labels. the text value for both the labels were written in OnPreRender method. However, i forgot to add control for one label in CreateChildControl method. So while debugging, i noticed that, after post back, the label whose control i forgot to add didn't retain the value and it was showing empty string.But the other label who's control i added was able to retain the value.
protected override void CreateChildControls()
{
base.CreateChildControls();
btnup.Text = " Update";
this.Controls.Add(lblid);//**If i add this, the label retains the value during post back , otherwise its null**
this.Controls.Add(lblname);
this.Controls.Add(lbldesig);
this.Controls.Add(tbdes);
this.Controls.Add(lblcomp);
this.Controls.Add(tbcomp);
this.Controls.Add(btnup);
btnup.Click += new EventHandler(btnup_Click);
}
protected override void OnPreRender(EventArgs e)
{
base.OnPreRender(e);
if (connectionInterface != null)
{
id = connectionInterface.parameter1;
SPWeb mysite = SPContext.Current.Web;
SPList mylist = mysite.Lists["UpdateList"];
SPListItemCollection itemcol = mylist.Items;
foreach (SPListItem itm in itemcol)
{
string nm = itm["Company_Id"].ToString();
if (nm.Equals(id))
{
lblid.Text = itm["Company_Id"].ToString();
lblname.Text = itm["Name"].ToString();
l
}
}
}
else
{
lblname.Text = "nothing is recieved!";
}
}
Why is it behaving like this?
This is a normal behavior. If you don't add the control to Controls collection, ASP.NET framework will not preserve its value in postback and hence will be lost during postback.