Unfortunately, Entity Framework 6 does not have built-in support for SQL Server Change Tracking. However, it does expose interception capabilities that enable you to modify the SQL it generates before execution. While changing the SQL an ORM generates is something that should be done carefully and only with good reason, there are absolutely cases where it is the appropriate solution.
EF6 exposes the IDbCommandInterceptor type, which gives you hooks into the entire query pipeline. You simple need to implement this interface and register your interceptor with EF.
Notably, the framework will call NonQueryExecuting before every INSERT, UPDATE, and DELETE, making it a great place for you to hook in your change tracking.
As a simple example, consider this interceptor:
public class ChangeTrackingInterceptor : IDbCommandInterceptor
{
private byte[] GetChangeTrackingContext()
{
// TODO: Return the appropriate change tracking context data
return new byte[] { 0, 1, 2, 3 };
}
public void NonQueryExecuting(DbCommand command, DbCommandInterceptionContext<int> interceptionContext)
{
command.CommandText = "WITH CHANGE_TRACKING_CONTEXT (@change_tracking_context)\r\n" + command.CommandText;
// Create the varbinary(128) parameter
var parameter = command.CreateParameter();
parameter.DbType = DbType.Binary;
parameter.Size = 128;
parameter.ParameterName = "@change_tracking_context";
parameter.Value = GetChangeTrackingContext();
command.Parameters.Add(parameter);
}
public void NonQueryExecuted(DbCommand command, DbCommandInterceptionContext<int> interceptionContext)
{
}
public void ReaderExecuting(DbCommand command, DbCommandInterceptionContext<DbDataReader> interceptionContext)
{
}
public void ReaderExecuted(DbCommand command, DbCommandInterceptionContext<DbDataReader> interceptionContext)
{
}
public void ScalarExecuting(DbCommand command, DbCommandInterceptionContext<object> interceptionContext)
{
}
public void ScalarExecuted(DbCommand command, DbCommandInterceptionContext<object> interceptionContext)
{
}
}
When EF generates any query that changes the state of the DB, it will call this method before executing the query. This gives you an opportunity to inject your custom change tracking context using standard SQL.
To register your interceptor with EF, simply call DbInterception.Add somewhere in your startup code:
var changeTrackingInterceptor = new ChangeTrackingInterceptor();
DbInterception.Add(changeTrackingInterceptor);
There's not a ton of great documentation on the IDbCommandInterceptor interface, but this MSDN article is a good place to start.
