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Gets or sets whether the object is locked; False if the object can be modified when the sheet is protected.
Use this property to control whether cells that use the style are locked when worksheet protection is enabled.
bool Locked { get; set; }
Property Locked As Boolean
IStyle style = workbook.Styles.Add("lockedStyle");
style.Locked = true;
worksheet.Range["A1"].Style = style;
bool locked = style.Locked;