如何覆盖默认 LINQ 到 SQL 关联名称

Question

I am working on a pretty straight forward C# application that uses LINQ to SQL for database access. The application is a non-web (ie thick client) application.

The problem that I have recently run into is with the default association name that LINQ to SQL is creating for fields that are foreign keys to another table. More specifically, I have provided an example below:

Example of Problem The majority of my combo boxes are filled using values from a reference data.table (ie RefData) that stores a type, description, and a few other fields. When the form initially loads, it fills the combo boxes with values based on a query by type. For example, I have a form that allows the user to add customers. On this form, there is a combo box for state. The stateComboBox is filled by running a query against the RefData.table where type = stateType. Then, when the user saves the customer with a selected state the id of the RefData column for the selected state is stored in the state column of the customer table. All of this works as expected. However, if my customer table has more than one column that is a foreign key to the RefData.table it quickly becomes very confusing because the association name(s) created by LINQ are Customer.RefData, Customer.RefData1, Customer.RefData2, etc... It would be much easier if I could override the name of the association so that accessing the reference data would be more like Customer.State, Customer.Country, Customer.Type, etc...

I have looked into changing this information in the DBML that is generated by VS but, my database schema is still very immature and constantly requires changes. Right now, I have been deleting the DBML every day or two to regenerate the LINQ to SQL files after making changes to the database. Is there an easy way to create these associations with meaningful names that will not be lost while I frequently re-create the DBML?

Answer 1

Create a partial class definition for your Customer table and add more meaningful getter properties for the LINQ to SQL generated member names:

public partial class Customer
{
    public string Name { get; set; }
    [JsonIgnore]
    public RefData State => this.RefData;
    [JsonIgnore] 
    public RefData Country => this.RefData1;
}

I blogged about this here

Answer 2

I am not sure LINQ to SQL is the best method of accessing data, period, but I find it even more problematic in your case.

Your real issue is you have the concept of your domain objects fairly static (you know what the program needs to use to get work done), but you are not sure how you are persisting the data, as your schema is in flux. This is not a good scenario for automagic updates.

If it were me, I would code the domain models so they do not change except when you desire change. I would then determine how to link to the persistent schema (database in this case). If you like a bit more automagic, then I would consider Entity Framework, as you can use code first and map to the schema as it changes.

If you find this still does not help, because your database schema changes are incompatible with the domain models, you need to get away from coding and go into a deeper planning mode. Otherwise, you are going to continue to beat your head against the proverbial wall of change.