如何实现从多个sql表读取的级联下拉列表？ C＃MVC

Question

I'm building an mvc web app using C#. The place I am currently stuck is trying to add a cascading drop-down list. I have seen several articles on this, however my usage varies enough that I'm not sure how to implement it.

My information to populate the dropdown lists is coming from a series of sql tables. The first dropdown should show the information from one table (which lists available tables). When the user selects an option, a second dropdown list should be created and filled with the information from the chosen table.

How would I implement this cascading dropdown list which could read from any number of different tables?

I believe this will involve AJAX/javascript which I'm not very familiar with.

To better explain my data structure, this is an application for an administrator to keep track of useful information. There could be several tables such as Employees, CompaniesWorkedWith, ProjectsBeingDeveloped, BudgetItems, etc... Then a final lookup table that would contain these table names. The first dropdown would be populated with information from this lookup table. Then when the user selects an item (such as Employee) the second dropdown would grab the information from the appropriate table and display it in a dropdown. Then the user could select and item (such as an individual employee) which will then grab the details of that item and present it to the user. That last part should be easy. I'm just confused on how to get the dropdowns to cascade through multiple tables. It should be dynamic that someone can easily go in and add another table to the lookup table and have it function properly.

Answer 1

You need to implement callback's to update the data sources for the cascaded controls. Just use your update panels appropriately to prevent full page post-backs. If you're using a framework such as DevExpress, Telerik or ASP.NET then there's lots of options and sample source code for this exact thing.

http://www.codeproject.com/Articles/730953/Cascading-Dropdown-List-With-MVC-LINQ-to-SQL-and-A

EDIT: I realized you're second data-source depends on a second more dynamic data source. To do this I would create my own data-source implmenting IEnumerable. I have a sample of something that may help somewhere... I'll look for it.

EDIT 2: Okay, I took a look at code similar to this (not quite the same) but here's how you can do it:

1. You'll need a generic container for your values for your second/third/etc. dropdown lists. This might be a List<string> or a List<MyGenericClass> with whatever properties you are filling out to represent your columns for each row in the dropdown.

2. Use SqlConnection , SqlCommand to iterate through the results and populate the List (or your own class that implements IEnumerable).

3. Assign the IEnumerable object to your dropdown list datasource.