修复BUG: SqlServer批导BulkInsert

/// <summary>
/// 使用SqlBulkCopy批导
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="entities"></param>
/// <param name="tableName"></param>
/// <returns></returns>
public override int BulkInsert<T>(List<T> entities, string tableName = null)
{
    using (SqlBulkCopy bulkCopy = CreateSqlBulkCopy())
    {
        bulkCopy.BatchSize = 5000;      // 每批处理行数
        bulkCopy.BulkCopyTimeout = 600; // 超时时间（秒）

        //获取实体类的表名
        if (String.IsNullOrEmpty(tableName))
        {
            var tableAttribute = (TableAttribute)typeof(T).GetCustomAttributes(typeof(TableAttribute), false).First();
            tableName = tableAttribute.Name;
        }

        //需要加dbo.
        if (!tableName.StartsWith("dbo")) tableName = "dbo." + tableName; 
        bulkCopy.DestinationTableName = tableName;

        //转换为DataTable
        var table = entities.ToDataTable();
        table.AcceptChanges();
        bulkCopy.WriteToServer(table);
        bulkCopy.Close();
        return table.Rows.Count;
    }
}