BulkUploadToSql.cs

 public class BulkUploadToSql<T>
{
    public IList<T> InternalStore { get; set; }
    public string TableName { get; set; }
    public int CommitBatchSize { get; set; } = 1000;
    public SqlConnection Connection { get; set; }

    public async Task Commit()
    {
        if (InternalStore.Count > 0)
        {
            DataTable dt;
            int numberOfPages = (InternalStore.Count / CommitBatchSize) +
                                (InternalStore.Count % CommitBatchSize == 0 ? 0 : 1);
            for (int pageIndex = 0; pageIndex < numberOfPages; pageIndex++)
            {
                dt = InternalStore.Skip(pageIndex * CommitBatchSize).Take(CommitBatchSize).ToDataTable();
                await BulkInsertAsync(dt);
            }
        }
    }

    public async Task BulkInsertAsync(DataTable dt)
    {
        SqlBulkCopy bulkCopy =
            new SqlBulkCopy
            (
                Connection,
                SqlBulkCopyOptions.TableLock |
                SqlBulkCopyOptions.FireTriggers |
                SqlBulkCopyOptions.UseInternalTransaction,
                null
            ) {DestinationTableName = TableName};

        await bulkCopy.WriteToServerAsync(dt);
    }

}

CallBulk.cs

var objBulk = new BulkUploadToSql<Client>()
{
    InternalStore = clients,
    TableName = "TableName",
    CommitBatchSize = 5000,
    Connection = conn
};