请问1,3两语句有何区别?不都是限制列的唯一性吗?是否重复?
DataTable1.Constraints.Add(new UniqueConstraint("Constraint1", new DataColumn[] {
DataTable1.columnItemId}, true));
DataTable1.columnItemId.AllowDBNull = false;
DataTable1.columnItemId.Unique = true;
DataTable1.Constraints.Add(new UniqueConstraint("Constraint1", new DataColumn[] {
DataTable1.columnItemId}, true));
DataTable1.columnItemId.AllowDBNull = false;
DataTable1.columnItemId.Unique = true;
DataTable1.columnItemId.Unique = true; //不单限止非空,且不允许重复
DataTable1.columnItemId.Unique = true; //不单限止非空,且不允许重复
DataTable1.columnItemId.Unique = true; //不单限止非空,且不允许重复DataTable1.columnItemId.AllowDBNull = false; //指只限止非空,允许重复值
DataTable1.columnItemId.Unique = true; //不单限止非空,且不允许重复DataTable1.columnItemId.AllowDBNull = false; //指只限止非空,允许重复值
DataTable1.columnItemId.Unique = true; //不单限止非空,且不允许重复DataTable1.columnItemId.AllowDBNull = false; //指只限止非空,允许重复值
DataTable1.columnItemId.Unique = true; //不单限止非空,且不允许重复DataTable1.columnItemId.AllowDBNull = false; //指只限止非空,允许重复值
DataTable1.columnItemId.Unique = true; //不单限止非空,且不允许重复
DataTable1.columnItemId.Unique = true; //不单限止非空,且不允许重复
DataTable1.columnItemId}, true));
和DataTable1.columnItemId.Unique = true;
的区别,呵呵