Programmatically use navigation properties in EF given the foreignkey

Question

In my project I use Entity Framework with ADO.NET. Suppose I have in Entity Framework the following classes:

class Product
{
   int Id { get; set;}
   string Name { get; set; }
   int TypeId { get; set; }
   int CategoryId { get; set; }
}

class Type
{
   int Id { get; set; }
   string Name { get; set; }
}

class Category
{
   int Id { get; set; }
   string Name { get; set; }
}

And then I have the navigation properties:

1. hasCategory: from Category(Id) to Product(CategoryId), 1 to Many
2. hasType: from Type(Id) to Product(TypeId), 1 to Many

Therefore if I want to access a specific category name or type name of a product (given the context):

int productId = 1;
var categoryName = context.Products.Single(p => p.Id == productId).hasCategory.Name;
var typeName = context.Products.Single(p => p.Id == productId).hasType.Name;

Now if I have the property name I can get the property:

string propertyName = "CategoryId";
var property = GetType(Product).GetProperty(propertyName)

Given the property I want to know if there is any way to get the matching navigation property (either hasCategory or hasType) in order to get the name. Oterwhise I do not know in which of the two classes Category and Type I should look for.

Answer 1

Hi Trinakriae,

Welcome to the MSDN forum.

If you mean the context and CategoryId are give, please check if the following helps:

            using (var context = new tstContext())
            {
                String propertyName = "CategoryId";
                Product p = context.Products.First();
                var name = p.GetType().BaseType.Name;

                var objectContext = ((IObjectContextAdapter)context).ObjectContext;
                var workspace = objectContext.MetadataWorkspace;
                var items = workspace.GetItems(System.Data.Metadata.Edm.DataSpace.CSpace);
                foreach (var item in items)
                {
                    EntityType entityType = item as EntityType;
                    if (entityType != null)
                    {
                        if (entityType.Name == name)
                        {
                            var navigationProperties = entityType.NavigationProperties;
                            foreach (var navigationProperty in navigationProperties)
                            {
                                Console.WriteLine("Navigation properties: {0}", navigationProperty.Name);
                                var properties = navigationProperty.GetDependentProperties();
                                foreach (var property in properties)
                                {
                                    Console.WriteLine("Foreign Key: {0}", property.Name);
                                    if (property.Name == propertyName)
                                    {
                                        Console.WriteLine("Matched!");
                                    }
                                }
                            }
                        }
                    }
                }
                Console.ReadLine();
            }

Have a nice day.

---

Alexander Sun [MSFT]
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