protected override string?GetSortExpression()
{
if (string.IsNullOrEmpty(SortExpression))
{
return(ValueBinding?.GetProperty <OriginalStringBindingProperty>()?.Code ??
throw new DotvvmControlException(this, $"The 'ValueBinding' property must be set on the '{GetType()}' control!"));
}
else
{
return(SortExpression);
}
}