Check out example codes for "!IsPostBack". It will help you in understanding the concepts better.

Code Example 1

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

Code Example 2

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

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