Is there an option to make Entity Framework revert empty strings to null?

Question

I am using an ADO.NET Entity-Framework ObjectContext to access my data store.

I want the if values are set with empty strings, they should automatically become null.

Answer 1

Just for completeness, here is the accepted answer written as a partial class instead of inherited. Note that this version also trims strings.

using System.Data;
using System.Data.Objects;
using System.Linq; 
public partial class MyObjectContext {
    private const string StringType = "String";
    private const EntityState SavingState = EntityState.Added | EntityState.Modified;

    public override int SaveChanges(SaveOptions options) {
        var savingEntries = this.ObjectStateManager.GetObjectStateEntries(SavingState);

        foreach (var entry in savingEntries) {
            var curValues = entry.CurrentValues;
            var fieldMetadata = curValues.DataRecordInfo.FieldMetadata;
            var stringFields = fieldMetadata.Where(f => f.FieldType.TypeUsage
                                                         .EdmType.Name == StringType);

            foreach (var stringField in stringFields) {
                var ordinal = stringField.Ordinal;
                var curValue = curValues[ordinal] as string;

                if (curValue != null && curValue.All(char.IsWhiteSpace)) {
                    curValues.SetValue(ordinal, null);
                }
                else if (curValue != null && curValue != curValue.Trim()) {
                    curValues.SetValue(ordinal, curValue.Trim());
                }
            }
        }
        return base.SaveChanges(options);
    }
}

I have also shown the required usings because I find it frustrating when I copy'n'paste code and the IDE throws up some errors about type or namespace not found.