i m not able to change precision of numeric datatype with SMO

I have created table using SMO object and i want to change precision of numeric datatype. Sometimes it gets changed but sometimes it is not and also do not generate any error.

Specially when i debug my code numeric precision do not change.

this is how i created my table

Code:
string connectionString = "Data Source = Server; Integrated Security = SSPI;";
                SqlConnection connection = new SqlConnection(connectionString);
                server = new Server(new ServerConnection(connection));
                Database db;
                db = server.Databases["Testing"];

Table mdtnewTable = new Table(db, "Testing0");
Column ColId = new Column(mdtnewTable, "Code0");
ColId.DataType = DataType.Numeric(0, 5);
ColId.Nullable = false;

Column ColId1 = new Column(mdtnewTable, "Code1");
ColId1.DataType = DataType.VarChar(50);
ColId1.Nullable = false;

Column ColName = new Column(mdtnewTable, "Name0");
ColName.DataType = DataType.VarChar(50);
ColNameS.Nullable = false;

mdtnewTable.Columns.Add(ColId);
mdtnewTable.Columns.Add(ColId1);
mdtnewTable.Columns.Add(ColName);

mdtnewTable.Create();

here is my code to change numeric precision

Code:
mdtnewTable = db.Tables["Testing0"];
Column ColId1 = mdtnewTable.Columns["Code0"];
ColId1.DataType = DataType.Numeric(0,10);
ColId1.Nullable = false;

mdtnewTable.Alter();
when i change numeric precision from 10 to any integer number say 15 and if i run my application without debugging than it's working fine. but when i debug it, it fails without giving any error message. There is no primary key
or any other contraints defined on this table

Plz help me