what is a ISpostBack code example

Example 1: !IsPostBack

private void Page_Load()
{
    if (!IsPostBack)
    {
        // Validate initially to force asterisks
        // to appear before the first roundtrip.
        Validate();
    }
}

Example 2: !IsPostBack

[System.ComponentModel.Browsable(false)]
public bool IsPostBack { get; }