how can I 'walk' the relationships between tables in LINQ?

问题

Let's say I have three tables:

Office
 ID 

SalespeopleOffice 
 ID 
 OfficeID
 PersonID

People 
 ID 
 ManagerID

In LINQ to SQL, how can I start from the SalespeopleOffices table and "walk" from that table to the People table or the Office table via the relationships between the tables? Specifically without knowing what those relationships are; pull the data about the relationships instead of interacting with the objects directly. I'm looking for a way to programatically analyze table relationships. The database I'm working with has many more tables than this, so in reality it's a lot more complex than this.

I'd ideally like to create a LinqPad script to do this.

回答1:

You can use reflection to examine the properties on each type in the context. (In LinqPad, the context is this).

Value and string properties will be scalar fields on the table,
EntitySet properties will represent [something]-to-many relationships, and
other types will be [something]-to-one relationships.

If you connect the two sides of the relationships you can figure out what the [something] is in each case. Does that make sense?

Edit

I was just poking around a little, and there's a better approach. The model information is available via the Mapping property. Try this:

var tableData = from t in this.Mapping.GetTables()
                select new 
                {
                    t.TableName,
                    Associations = 
                        from a in t.RowType.Associations
                        select new
                    {
                        a.ThisMember.Name,
                        TypeName = a.ThisMember.Type.Name
                    }
                };
tableData.Dump();

Assuming you've activated Auto Completion, it should be a piece of cake to find the exact data you're interested in by exploring the properties on this meta data.

回答2:

If you're using LINQ to SQL, your SalespeopleOffices instances shoud have People and Office properties.

Something like:

var salesPO = dataContext.SalespeopleOffices.First()
var office = salesPO.Office 
var man = salesPO.People

来源：https://stackoverflow.com/questions/4380834/how-can-i-walk-the-relationships-between-tables-in-linq

标签

linq

linq-to-sql

linqpad