Generically correcting data before save with Entity Framework
- by koevoeter
Been working with Entity Framework (.NET 4.0) for a week now for a data migration job and needed some code that generically corrects string values in the database. You probably also have seen things like empty strings instead of NULL or non-trimmed texts ("United States ") in "old" databases, and you don't want to apply a correcting function on every column you migrate.
Here's how I've done this (extending the partial class of my ObjectContext):public partial class MyDatacontext{ partial void OnContextCreated() { SavingChanges += OnSavingChanges; } private void OnSavingChanges(object sender, EventArgs e) { foreach (var entity in GetPersistingEntities(sender)) { foreach (var propertyInfo in GetStringProperties(entity)) { var value = (string)propertyInfo.GetValue(entity, null); if (value == null) { continue; } if (value.Trim().Length == 0 && IsNullable(propertyInfo)) { propertyInfo.SetValue(entity, null, null); } else if (value != value.Trim()) { propertyInfo.SetValue(entity, value.Trim(), null); } } } }
private IEnumerable<object> GetPersistingEntities(object sender) { return ((ObjectContext)sender).ObjectStateManager .GetObjectStateEntries(EntityState.Added | EntityState.Modified)
.Select(e => e.Entity); } private IEnumerable<PropertyInfo> GetStringProperties(object entity) { return entity.GetType().GetProperties() .Where(pi => pi.PropertyType == typeof(string)); } private bool IsNullable(PropertyInfo propertyInfo) { return ((EdmScalarPropertyAttribute)propertyInfo
.GetCustomAttributes(typeof(EdmScalarPropertyAttribute), false) .Single()).IsNullable; }}
Obviously you can use similar code for other generic corrections.
