The SessionStateItemCollection.Dirty property is used to indicate whether the contents of the System.Web.SessionState.SessionStateItemCollection collection have changed.

The SessionStateItemCollection.Dirty property is set to true when an object value is set or added to the collection using the erload:System.Web.SessionState.SessionStateItemCollection.Item property and when one or more object values are removed from the collection using the SessionStateItemCollection.Remove(string), SessionStateItemCollection.RemoveAt(int), or SessionStateItemCollection.Clear methods.

The SessionStateItemCollection.Dirty property is also set to true when a mutable object is retrieved from the collection using the erload:System.Web.SessionState.SessionStateItemCollection.Item property.

Calling the SessionStateItemCollection.Deserialize(System.IO.BinaryReader) method to populate a System.Web.SessionState.SessionStateItemCollection collection results in the SessionStateItemCollection.Dirty property being set to false.