LINQ to Entities-更新二进制字段

Question

I have LINQ to Entities set up with MySQL.

One field is a binary type, for example varbinary(50).

LINQ to Entities returns this correctly as a byte[].

However, if I just change the value of one index in the byte[], the change is not propagated to the database when SaveChanges() is called.

For example, this doesn't work:

byte[] foo = GetBinaryFromDatabase(context);
foo[0] = 42;
context.SaveChanges();

I can get it to save the changes by creating an entirely new byte array, copying it over and assigning it back rather than doing it in-place.

For example, this works:

byte[] foo = GetBinaryFromDatabase(context);
byte[] bar = new byte[foo.Length];
Array.Copy(foo, bar, foo.Length);
bar[0] = 42;
foo = bar;
context.SaveChanges();

Is there any way to make the change in-place without having to make a copy of the array, such that it propagates to the database? For example, to mark that byte[] as dirty (or a better solution)?

Answer 1

You can mark a property as modified like this:

var entry = context.Entry(foo);

if (entry.State == EntityState.Detached)
    context.Set<FooType>().Attach(entity);

entry.Property(e => e.ByteProperty).IsModified = true;

// Or this if your version of EF doesn't support the lambda version:
// entry.Property("ByteProperty").IsModified = true;

I suspect it is looking for the property actually being set in order to mark it as modified rather than modifying the contents of the property (like you suspect).