Update a record without first querying?

You can also use direct SQL against the database using the context of the datastore. Example:

dataEntity.ExecuteStoreCommand
   ("UPDATE items SET itemstatus = 'some status' WHERE id = 123 ");

For performance reasons, you may want to pass in variables instead of a single hard coded SQL string. This will allow SQL Server to cache the query and reuse with parameters. Example:

dataEntity.ExecuteStoreCommand
   ("UPDATE items SET itemstatus = 'some status' WHERE id = {0}", new object[] { 123 });

UPDATE - for EF 6.0

dataEntity.Database.ExecuteSqlCommand
       ("UPDATE items SET itemstatus = 'some status' WHERE id = {0}", new object[] { 123 });

You should use the Attach() method.

Attaching and Detaching Objects

If the DataItem has fields EF will pre-validate (like non-nullable fields), we'll have to disable that validation for this context:

DataItem itemToUpdate = new DataItem { Id = id, Itemstatus = newStatus };
dataEntity.Entry(itemToUpdate).Property(x => x.Itemstatus).IsModified = true;
dataEntity.Configuration.ValidateOnSaveEnabled = false;
dataEntity.SaveChanges();
//dataEntity.Configuration.ValidateOnSaveEnabled = true;

Otherwise we can try satisfy the pre-validation and still only update the single column:

DataItem itemToUpdate = new DataItem
{
    Id = id,
    Itemstatus = newStatus,
    NonNullableColumn = "this value is disregarded - the db original will remain"
};
dataEntity.Entry(itemToUpdate).Property(x => x.Itemstatus).IsModified = true;
dataEntity.SaveChanges();

Assuming dataEntity is a System.Data.Entity.DbContext

You can verify the query generated by adding this to the DbContext:

/*dataEntity.*/Database.Log = m => System.Diagnostics.Debug.Write(m);

The code:

ExampleEntity exampleEntity = dbcontext.ExampleEntities.Attach(new ExampleEntity { Id = 1 });
exampleEntity.ExampleProperty = "abc";
dbcontext.Entry<ExampleEntity>(exampleEntity).Property(ee => ee.ExampleProperty).IsModified = true;
dbcontext.Configuration.ValidateOnSaveEnabled = false;
dbcontext.SaveChanges();

The result TSQL:

exec sp_executesql N'UPDATE [dbo].[ExampleEntities]
SET [ExampleProperty ] = @0
WHERE ([Id] = @1)
',N'@0 nvarchar(32),@1 bigint',@0='abc',@1=1

Note:

The "IsModified = true" line, is needed because when you create the new ExampleEntity object (only with the Id property populated) all the other properties has their default values (0, null, etc). If you want to update the DB with a "default value", the change will not be detected by entity framework, and then DB will not be updated.

In example:

exampleEntity.ExampleProperty = null;

will not work without the line "IsModified = true", because the property ExampleProperty, is already null when you created the empty ExampleEntity object, you needs to say to EF that this column must be updated, and this is the purpose of this line.