Determine Whether a Table Has an Identity Column

SQL Server 2005+

SELECT OBJECTPROPERTY(object_id('TableToBeChecked'), 'TableHasIdentity')

SMO

Server srv = new Server("(local)");
Database db = srv.Databases["AdventureWorks2012"];

Table tb = new Table(db, "Test Table");
Column col1 = new Column(tb, "TableIdentifier", DataType.Int);
col1.Identity = true;
tb.Columns.Add(col1); 

try

{

foreach (String s in tb.CheckIdentityValue())

{
   Console.WriteLine(s);
}

}

catch

{

}