Question

i have two user controls uc1 and uc2.
uc1 as button and uc2 has label,
so default.aspx contain both uc1 and uc2,
How can i change value of label by clicking on button???
remember both are in the different user control.

Answer 1

Try to use FindControl method of your page and get the control that has the label, and set the text to this control by an exposed property.

// On your button's click : 
UserControl2 uc2 = Page.FindControl("uc2") as UserControl2;
uc2.LabelText = "Some Value";