SqlBulkCopy - Unexpected existing transaction

Question

I am using SqlBulkCopy to insert large amount of data:

try
{
   using (var bulkCopy = new SqlBulkCopy(connection))
   {
      connection.Open();

      using (var tran = connection.BeginTransaction(IsolationLevel.ReadCommitted))
      {
          bulkCopy.DestinationTableName = "table";

          bulkCopy.ColumnMappings.Add("...", "...");                            

          using (var dataReader = new ObjectDataReader<MyObject>(data))
          {
              bulkCopy.WriteToServer(dataReader);
          }

          tran.Commit();
          return true;
      }
   }
}
catch (Exception ex)
{
    return false;
}

But I always get exception:

Unexpected existing transaction.

Why this exception happens?

Answer 1

"Unexpected existing transaction" ... Why this exception happens?

This happens because using the SqlBulkCopy constructor without specifying a transaction will create its own transaction internally.

Avoid this by creating your transaction and then use it to create the SqlBulkCopy . SqlBulkCopy can be created with the transaction that you want to use, like this:

connection.Open();
using (var tran = connection.BeginTransaction(IsolationLevel.ReadCommitted))
{
    using (var bulkCopy = new SqlBulkCopy(connection, SqlBulkCopyOptions.Default, tran))
    {

Answer 2

You need to use the constructor that takes in the transaction so SqlBulkCopy will be aware of the transaction

connection.Open();

using (var tran = connection.BeginTransaction(IsolationLevel.ReadCommitted))
{
   using (var bulkCopy = new SqlBulkCopy(connection, SqlBulkCopyOptions.Default, tran))
   {
       bulkCopy.DestinationTableName = "table";

       bulkCopy.ColumnMappings.Add("...", "...");                            

       using (var dataReader = new ObjectDataReader<MyObject>(data))
       {
          bulkCopy.WriteToServer(dataReader);
       }

       tran.Commit();
       return true;

   }
}