public SaveConstraintAttribute(SaveConstraint behaviour)
{
Behaviour = behaviour;
}
/// <summary>
/// Adds entity to corresponding db set if an entity with same primary key does not exist in database,
/// or updates existing instance with the same primary key.
/// </summary>
/// <typeparam name="TEntity">Entity class</typeparam>
/// <param name="ctx">Context instance</param>
/// <param name="entity">Entity instance to add or update.</param>
public static void AddOrUpdateEntity <TEntity>(this DbContext ctx, TEntity entity) where TEntity : class
{
Type clrType = typeof(TEntity);
EntityType entityType = ctx.GetEntityType(clrType);
if (entityType == null)
{
throw new ArgumentException($"Class `{clrType.Name}` is not an entity type for database context {ctx.GetType().Name}.");
}
// name of key property
string keyPropertyName = entityType.KeyProperties.First().Name;
// key property
PropertyInfo keyProperty = clrType.GetProperty(keyPropertyName);
// key value
object key = keyProperty.GetValue(entity);
// Create "e" portion of lambda expression
ParameterExpression parameter = Expression.Parameter(clrType, "e");
// create "e.Id" portion of lambda expression
MemberExpression expProperty = Expression.Property(parameter, keyProperty.Name);
// create "'id'" portion of lambda expression
var expKeyConstant = Expression.Constant(key);
// create "e.Id == 'id'" portion of lambda expression
var expEqual = Expression.Equal(expProperty, expKeyConstant);
// finally create entire expression: "e => e.Id == 'id'"
Expression <Func <TEntity, bool> > predicate = Expression.Lambda <Func <TEntity, bool> >(expEqual, new[] { parameter });
// search existing entity
var existing = ctx.QueryEntitiesWithRelated <TEntity>().FirstOrDefault(predicate);
if (existing != null)
{
var navProperties = entityType.NavigationProperties.Select(np => ctx.Entry(entity).Member(np.Name)).ToArray();
var collectionNavProperties = navProperties.OfType <DbCollectionEntry>().ToArray();
if (collectionNavProperties.Any())
{
UpdateRelatedCollections(ctx, existing, entity, collectionNavProperties);
}
var singleNavProperties = navProperties.OfType <DbReferenceEntry>().Where(np => np.CurrentValue != null).ToArray();
foreach (var navProperty in singleNavProperties)
{
ctx.Entry(navProperty.CurrentValue).State = EntityState.Added;
}
ctx.Entry(existing).CurrentValues.SetValues(entity);
}
else
{
ctx.Set <TEntity>().Add(entity);
}
var saveBehaviourProperties = clrType.GetProperties().Where(p => p.CustomAttributes.Any(a => a.AttributeType == typeof(SaveConstraintAttribute))).ToList();
foreach (var property in saveBehaviourProperties)
{
SaveConstraint constraint = property.GetCustomAttribute <SaveConstraintAttribute>().Behaviour;
var edmMember = entityType.DeclaredMembers.First(p => p.Name == property.Name);
// do not modify property if new value is default value
if (constraint == SaveConstraint.NotEmpty && GetDefaultValueOfType(property.PropertyType) == property.GetValue(entity))
{
if (edmMember.BuiltInTypeKind == BuiltInTypeKind.NavigationProperty)
{
// do nothing, navigation property with null value not saved by default
}
else if (edmMember.BuiltInTypeKind == BuiltInTypeKind.EdmProperty)
{
ctx.Entry(existing).Property(property.Name).IsModified = false;
}
}
// do not modify property if it's a referenced entity and it's already exist in db
if (constraint == SaveConstraint.NotExists && existing != null)
{
if (edmMember.BuiltInTypeKind == BuiltInTypeKind.NavigationProperty)
{
object newPropertyValue = property.GetValue(entity);
object existingPropertyValue = ctx.SearchEntityByKey(newPropertyValue);
if (newPropertyValue != null && existingPropertyValue != null)
{
ctx.Entry(newPropertyValue).State = EntityState.Detached;
}
}
else if (edmMember.BuiltInTypeKind == BuiltInTypeKind.EdmProperty)
{
throw new Exception($"{property.Name} property of type {clrType.Name} is not navigation property. {nameof(SaveConstraint.NotExists)} constraint can be applied for navigation properties only.");
}
}
// do not save properties marked with "Never"
if (constraint == SaveConstraint.Never)
{
if (edmMember.BuiltInTypeKind == BuiltInTypeKind.NavigationProperty)
{
object newPropertyValue = property.GetValue(entity);
if (newPropertyValue != null)
{
ctx.Entry(newPropertyValue).State = EntityState.Detached;
}
}
else if (edmMember.BuiltInTypeKind == BuiltInTypeKind.EdmProperty)
{
ctx.Entry(existing).Property(property.Name).IsModified = false;
}
}
}
}
