when i need sql command builder

The SqlDataAdapter does not automatically generate the Transact-SQL statements required to reconcile changes made to a DataSet with the associated instance of SQL Server. However, you can create a SqlCommandBuilder object to automatically generate Transact-SQL statements for single-table updates if you set the SelectCommand property of the SqlDataAdapter. Then, any additional Transact-SQL statements that you do not set are generated by the SqlCommandBuilder.

The SqlCommandBuilder registers itself as a listener for RowUpdating events whenever you set the DataAdapter property. You can only associate one SqlDataAdapter or SqlCommandBuilder object with each other at one time.

To generate INSERT, UPDATE, or DELETE statements, the SqlCommandBuilder uses the SelectCommand property to retrieve a required set of metadata automatically. If you change the SelectCommand after the metadata has been retrieved, such as after the first update, you should call the RefreshSchema method to update the metadata.

The SelectCommand must also return at least one primary key or unique column. If none are present, an InvalidOperation exception is generated, and the commands are not generated.

The SqlCommandBuilder also uses the Connection, CommandTimeout, and Transaction properties referenced by the SelectCommand. The user should call RefreshSchema if one or more of these properties are modified, or if the SelectCommand itself is replaced. Otherwise the InsertCommand, UpdateCommand, and DeleteCommand properties retain their previous values.

If you call Dispose, the SqlCommandBuilder is disassociated from the SqlDataAdapter, and the generated commands are no longer used.

When you need it. If you want a better answer you'll have to do a little better with the question.