如何在单击同一按钮时更新和读取 sql 列的值

Question

我正在做的是单击一个按钮，我正在通过向其添加 +1 来更新 sql 列。这样做我没有遇到任何问题。现在我想要的是，对于同一个按钮单击事件，我想读取我已更新的那一列的值，并将其在查询字符串中发送到另一个页面。这是代码-

int i=0;
protected void btnSubmit_Click(object sender, EventArgs e)
{
    sql.Open();
    string r = "update counter set m_id=m_id+1 where id=1";
    SqlCommand com = new SqlCommand(r, sql);
    com.ExecuteNonQuery();
    sql.Close();
    {
        SendHTMLMail();
    }





void SendHTMLMail()
{
    StreamReader reader = new StreamReader(dd1.SelectedItem.Value);
    string readFile = reader.ReadToEnd();
    Regex regx = new Regex("(?<!src=\")http(s)?://([\w+?\.\w+])+([a-zA-Z0-9\~\!\@\#\$\%\^\&amp;\*\(\)_\-\=\+\\\/\?\.\:\;\'\,]*([a-zA-Z0-9\?\#\=\/]){1})?", RegexOptions.IgnoreCase);
    string output = regx.ToString();    
    string count = 0.ToString();
    output = readFile;
    string username = Server.UrlEncode(this.txtUsername.Text);

    //here i want to read the value of m_id that i have updated as shown above and setting it to 'i' and passing this i  to the query string//

    sql.Open();
    string re = "select m_id from counter where id=1";
    SqlCommand ccmd = new SqlCommand(re, sql);
    com.ExecuteNonQuery();
    SqlDataReader read = ccmd.ExecuteReader();
    {
       while (read.Read())
          i =int.Parse(read["m_id"].ToString());

    }
    sql.Close();

    output = regx.Replace(output, new MatchEvaluator((match) =>
    {   
      var url = Uri.EscapeDataString(match.Value.ToString());
      return $"http://localhost:61187/two?sender={username}&link={url}&count={count}&mailer_id={i}";
    }));

现在，问题不是从 5 更新到 6，而是 m_id 更新到 7

Answer 1

您可以批处理 命令，只执行一个命令而不是调用数据库两次

protected void btnSubmit_Click(object sender, EventArgs e)
{
    sql.Open();
    string r = @"update counter set m_id=m_id+1 where id=1;
                 select m_id from counter where id=1;";

    SqlCommand com = new SqlCommand(r, sql);
    int result = (int)com.ExecuteScalar();
    sql.Close();
    {
        SendHTMLMail(result);
    }
}

此时 SendHTMLMail 方法（嵌套或非嵌套）可以接收 result 变量并避免对数据库引擎的任何调用。请注意，在这种情况下，我已将 ExecuteNonQuery 更改为 ExecuteScalar 以取回 select.

返回的唯一值

但是，如果仍然希望将事物分开，那么您需要将 SendHTMLMail 中的代码更改为类似这样的代码

// just change the CommandText to avoid reexecuting the INSERT
com.CommandText = "select m_id from counter where id=1";

// No more needed
// SqlCommand ccmd = new SqlCommand(re, sql);

// Get the reader from the SqlCommand
SqlDataReader read = com.ExecuteReader();
{
    .... go on with reading

如何在单击同一按钮时更新和读取 sql 列的值

how to update and read the value of sql column on click of the same button

.net

sql-server

sql-update

reader