ADO.NET :: How To Execute Alter Table For Multiple Columns

I have an SQL table called tbl, im trying to add the columns A, B and C to it.

When i execute the command :

addcolumns = "ALTER TABLE SqlCreatedTbl ADD A char(50) ;";
cmd = new SqlCommand(addcolumns, conn);
conn.Open(); cmd.ExecuteNonQuery();

The column is added perfectly and i can see it in the table !

However, when i try to add multiple columns, it does NOT work, it gives me an error..

the command im writting for adding multiple columns is the following:

addcolumns = "ALTER TABLE SqlCreatedTbl ADD ( A char(50), B char(50), C char(50) );";

the debugger highlights the line : cmd.ExecuteNonQuery(); and throws the following exception: Exception Details: System.Data.SqlClient.SqlException: Incorrect syntax near '('.