Issue_21: Added logic to SqliteForeignKeyIndexConvention.

Todo: - Encapsulate index name generation
- More Column indicies

Author: msallin

SQLite.CodeFirst/Convention/SqliteForeignKeyIndexConvention.cs

@@ -1,12 +1,18 @@
 using System;
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations.Schema;
 using System.Data.Entity.Core.Metadata.Edm;
 using System.Data.Entity.Infrastructure;
+using System.Data.Entity.Infrastructure.Annotations;
 using System.Data.Entity.ModelConfiguration.Conventions;
+using System.Linq;
 
 namespace SQLite.CodeFirst.Convention
 {
     public class SqliteForeignKeyIndexConvention : IStoreModelConvention<AssociationType>
     {
+        private const string IndexAnnotationName = "http://schemas.microsoft.com/ado/2013/11/edm/customannotation:Index";
+
         public virtual void Apply(AssociationType item, DbModel model)
         {
             if (item == null)
@@ -21,6 +27,44 @@ public virtual void Apply(AssociationType item, DbModel model)
             {
                 return;
             }
+
+            for (int i = 0; i < item.Constraint.ToProperties.Count; i++)
+            {
+                EdmProperty edmProperty = item.Constraint.ToProperties[i];
+                var annotation = GetAnnotation(edmProperty.MetadataProperties, IndexAnnotationName);
+                if (annotation != null)
+                {
+                    // The original attribute is removed. The noneForeignKeyIndicies will be remained and readded without any modification
+                    // and the foreignKeyIncidies will be readded with the correct name.
+                    edmProperty.RemoveAnnotation(IndexAnnotationName);
+
+                    var noneForeignKeyIndicies = annotation.Indexes.Where(index => index.Name != "IX_" + edmProperty.Name);
+                    IndexAnnotation newIndexAnnotation = new IndexAnnotation(noneForeignKeyIndicies);
+
+                    var foreignKeyIndicies = annotation.Indexes.Where(index => index.Name == "IX_" + edmProperty.Name);
+                    foreach (var foreignKeyIndex in foreignKeyIndicies)
+                    {
+                        var indexAttribute = new IndexAttribute(string.Format("IX_{0}_{1}", item.Constraint.ToRole.Name, edmProperty.Name));
+                        IndexAnnotation foreignKeyIndexAnnotation = new IndexAnnotation(indexAttribute);
+                        newIndexAnnotation = (IndexAnnotation)newIndexAnnotation.MergeWith(foreignKeyIndexAnnotation);
+                    }
+
+                    edmProperty.AddAnnotation(IndexAnnotationName, newIndexAnnotation);
+                }
+            }
+        }
+
+
+        private static IndexAnnotation GetAnnotation(IEnumerable<MetadataProperty> metadataProperties, string name)
+        {
+            foreach (MetadataProperty metadataProperty in metadataProperties)
+            {
+                if (metadataProperty.Name.Equals(name, StringComparison.Ordinal))
+                {
+                    return (IndexAnnotation)metadataProperty.Value;
+                }
+            }
+            return null;
         }
     }
 }