问题描述

我正在 ADO.NET 中手动编写事务代码.我正在使用的示例重用了 SqlCommand，这看起来是个好主意.

I'm coding a transaction manually in ADO.NET. The example I'm working from reuses the SqlCommand which seem like a fine idea.

但是，我在命令中添加了参数.

However, I have added parameters to my command.

我的问题是:在下面的代码中，command.Parameters.Clear() 是否正确?还是我做错了?

My question is: in the following code, is command.Parameters.Clear() correct? Or am I doing it wrong?

using (var connection = new SqlConnection(EomAppCommon.EomAppSettings.ConnStr))
{
    connection.Open();
    SqlTransaction transaction = connection.BeginTransaction();
    SqlCommand command = connection.CreateCommand();
    command.Transaction = transaction;
    try
    {
        foreach (var itemIDs in this.SelectedItemIds)
        {
            command.CommandText = "UPDATE Item SET payment_method_id = @batchID WHERE id in (@itemIDs)";
            // IS THE FOLLOWING CORRECT?
            command.Parameters.Clear();

            command.Parameters.Add(new SqlParameter("@batchID", batchID));
            command.Parameters.Add(new SqlParameter("@itemIDs", itemIDs));
            command.ExecuteNonQuery();
        }
        transaction.Commit();
    }
    catch (Exception ex)
    {
        MessageBox.Show("Failed to update payment batches, rolling back." + ex.Message);
        try
        {
            transaction.Rollback();
        }
        catch (Exception exRollback)
        {
            if (!(exRollback is InvalidOperationException)) // connection closed or transaction already rolled back on the server.
            {
                MessageBox.Show("Failed to roll back. " + exRollback.Message);
            }
        }
    }
}

推荐答案

由于您重复执行相同的查询，因此没有必要清除它们 - 您可以将参数添加到循环外，只需将它们填充到内即可.

Since you're repeatedly executing the same query, it's unnecessary to clear them - you can add the parameters outside the loop and just fill them inside.

try
{
    command.CommandText = "UPDATE Item SET payment_method_id = @batchID WHERE id in (@itemIDs)";
    command.Parameters.Add(new SqlParameter("@batchID", 0));
    command.Parameters.Add(new SqlParameter("@itemIDs", ""));

    foreach (var itemIDs in this.SelectedItemIds)
    {
        command.Parameters["@batchID"].Value = batchID;
        command.Parameters["@itemIDs"].Value = itemIDs;
        command.ExecuteNonQuery();
    }
    transaction.Commit();
}

注意 - 您不能在此处使用带有 IN 的参数 - 它不会工作.

Note - you can't use parameters with IN as you've got here - it won't work.