Question

I’m creating a C# T4 template to scaffold some classes based on .edmx file, so far so good. What I now need though, is a way to access the name of the columns it connects in the database, through a NavigationProperty.

I realized, not long ago, that you can access this information in the .edmx visual designer, under mapping details for an specific NavigationProperty:

So basically, if in the T4 template; I already have an instance of the NavigationProperty I want… How can I get the names of the fields it connects? (WeatherOnMondays in this case)

Answer 1

Answers from: EF4: Get the linked column names from NavigationProperty of an EDMX

2 ways of achieving this:

// Obtain a reference to the navigation property you are interested in
var navProp = GetNavigationProperty();
// Load the metadata workspace
MetadataWorkspace metadataWorkspace = null;
bool allMetadataLoaded =loader.TryLoadAllMetadata(inputFile, out metadataWorkspace);

// Get the association type from the storage model
var association = metadataWorkspace
    .GetItems<AssociationType>(DataSpace.SSpace)
    .Single(a => a.Name == navProp.RelationshipType.Name)

// Then look at the referential constraints
var toColumns = String.Join(",", 
    association.ReferentialConstraints.SelectMany(rc => rc.ToProperties));
var fromColumns = String.Join(",", 
    association.ReferentialConstraints.SelectMany(rc => rc.FromProperties));

2nd approach:

NavigationProperty[] foreignKeys = entity.NavigationProperties
  .Where(np => np.DeclaringType == entity &&
          ((AssociationType)np.RelationshipType).IsForeignKey).ToArray();

foreach (NavigationProperty foreignKey in foreignKeys)
{
   foreach(var rc in GetSourceSchemaTypes<AssociationType>()
       .Single(x => x.Name == foreignKey.RelationshipType.Name)
       .ReferentialConstraints)
   {
       foreach(var tp in rc.ToProperties)
           WriteLine(tp.Name);
       foreach(var fp in rc.FromProperties)
           WriteLine(fp.Name);
   }
}