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.NET Forum / Windows Forms / WinForm General / July 2004Lookup tables and data binding
Hello, I have a form that is used only to insert data into a database. It is composed of a datagrid which is used only for displaying data and selecting rows and a few text and combo boxes for the actual data editing. What I want to do is bind these to a data source, but I am not exactly sure how to handle the comboboxes which show data from a standard lookup table (int id, nvarchar something). I displayed data from lookup tables by binding their ValueMember and DataMember properties. When the user clicks a row in the datagrid, the data from that row should appear in the other controls for editing. The comboboxes should show the data from the selected row, but how can they do this if they are already bound to lookup tables? A possible workaround is to bind the comboboxes to the lookup tables when a new record is being created, and to the datagrid's datasource later. This has its own share of problems, of course. Maybe I should describe these relations in a dataset, and rely on the data binding mechanism to figure out what is supposed to be in the combo boxes? The problem with this is that I do not need a SELECT statement, because this form is write-only. What do I do with the DataAdapter.Fill() and DataAdapter.SelectCommand then? I hope I made myself clear. If any clarifications are needed, do not hesitate to ask. Regards, Joe > When the user clicks a row in the datagrid, the data from that row should > appear in the other controls for editing. The comboboxes should show the > data from the selected row, but how can they do this if they are already > bound to lookup tables? I think you're clear enough... Let's find out. The binding of the ComboBox to a lookup table is actually separate from the selection, as it should be. I think you probably want to keep your DisplayMember and ValueMember settings as they are, but to add a binding for SelectedValue to the underlying table. This would be to the column which holds the lookup value, i.e. the FK reference. So you have two "bindings" - one to the lookup table (DataSource, DisplayMember and ValueMember), and one to the actual table (SelectedValue). The trick is that DataSource in this case is unrelated to data bindings - it's only indicating where the list comes from. When you mention values from the datagrid row appearing in the other controls for editing, this appears to be at odds with the notion that the form is only used for adding data. Are the datagrid rows serving as default values or something? Best Regards, Andy > So you have two "bindings" - one to the lookup table (DataSource, > DisplayMember and ValueMember), and one to the actual table (SelectedValue). > The trick is that DataSource in this case is unrelated to data bindings - > it's only indicating where the list comes from. Thanks, that's it! > When you mention values from the datagrid row appearing in the other > controls for editing, this appears to be at odds with the notion that the > form is only used for adding data. Are the datagrid rows serving as default > values or something? The user can insert, delete and update rows locally, in the memory, but once finished, the final data is inserted into the database. So, there really are only INSERT operations going on. Is there a way to easily create a DataTable that has the same structure as a physical table in the database? Since there is no SELECT on this form which would get me the DataTable to use as a data source, I have to manually create one which has the same schema as the one in the database. I know about DataReader.GetSchemaTable(), but is there a way to automatically "apply" that information to a DataTable? Am I missing something obvious (again)? Thanks for the help. > Is there a way to easily create a DataTable that has the same structure as a > physical table in the database? Since there is no SELECT on this form which [quoted text clipped - 3 lines] > "apply" that information to a DataTable? Am I missing something obvious > (again)? I would use a typed dataset, if you don't mind creating it at compile time. In Solution Explorer, right click the project and then Add New Item. Choose Dataset, name this puppy whatever you like, and then you will get a design surface. From Server Explorer (same tool window as Toolbox, by default), create a data connection to the DB. Then if you drag the table onto the design surface, it will create a typed dataset for you, PK definition and all, matching the table. If you are talking about creating the table at runtime, I'm not sure how it would be done. Clearly it can though, since the IDE does it in the steps I just described. Best Regards, Andy > If you are talking about creating the table at runtime, I'm not sure how it > would be done. Clearly it can though, since the IDE does it in the steps I > just described. Creating it at runtime is what I meant, but I managed to work around this problem. Thank you very much for your extensive replies. Joe Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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