Determine if property is a Navigation Property in EF Core

问题

I'm building a simple change tracker to capture all the edits to a Sql Azure database (unfortunately, Sql Azure doesn't support this natively, so far as I can tell).

I'm walking the list of modified entries returned by ChangeTracker():

foreach( EntityEntry entry in _context.ChangeTracker.Entries()
    .Where( e => e.State == EntityState.Modified ) )
{
    foreach( var prop in entry.Entity
        .GetType()
        .GetTypeInfo()
        .DeclaredProperties ) 
    {
        // this line blows up on navigation properties
        PropertyEntry propEntry = entry.Property( prop.Name );

        if( propEntry.IsModified )
        {
            var curValue = entry.Property( prop.Name ).CurrentValue;
            var origValue = entry.Property( prop.Name ).OriginalValue;
        }
    }
}

Unfortunately, retrieving the PropertyEntry info for a property blows up -- InvalidOperationException -- when the property is a navigation property, claiming the property can't be found.

I could just wrap the code in an try/catch block...but I'm curious if there's another way to determine, perhaps from metadata, that a property is a navigation or related property.

回答1:

Rather than using reflection

foreach (var prop in entry.Entity.GetType().GetTypeInfo().DeclaredProperties)

you can use the metadata provided by the EntityEntry.Metadata property:

foreach (var prop in entry.Metadata.GetProperties())

Note that the IEntityType returned by the Metadata property has separate methods for simple properties (GetProperties method) and navigation properties (GetNavigations extension method).

来源：https://stackoverflow.com/questions/39862358/determine-if-property-is-a-navigation-property-in-ef-core

标签

entity-framework-core