如何将SQL中特定列的数据导入C＃中的标签？ [英] How do I import data from a particular column in SQL to label in C#?

问题描述

您好，



我正在尝试从SQL Server中的表中获取数据到我的Windows窗体中的Label。它显示我一个空的异常错误，我无法弄清楚原因。


我收到此错误：

System.IndexOutOfRangeException：'@Name'位于以下行：

NameLabel.Text = reader [@ Name]。ToString（）;



我将它存储在字符串中，因为我以另一种形式调用该值。



请帮助。



我的尝试：

Hello,

I am trying to fetch data from a table in SQL Server to Label in my Windows Form. It is showing me a null exception error and I am unable to figure out why.

I am getting this error:
System.IndexOutOfRangeException: '@Name' on the following line:
NameLabel.Text = reader["@Name"].ToString();

I am storing it in a string because I am calling the value in another form.

Please help.

What I have tried:

string queryText = @"SELECT Count(*) FROM NewsClip_Login 
                             WHERE Username = @Username AND Password = @Password";

                using (SqlConnection cn = new SqlConnection("Data Source=PRIMO-CHALICE;Initial Catalog=NewsClip;Integrated Security=True"))
                using (SqlCommand cmd = new SqlCommand(queryText, cn))
                {
                    cn.Open();
                    cmd.Parameters.AddWithValue("@Username", UsernameTextBox.Text);
                    cmd.Parameters.AddWithValue("@Password", PasswordTextBox.Text);
                    cmd.Parameters.AddWithValue("@Name", NameLabel.Text);
                    SqlDataReader reader = cmd.ExecuteReader();

                    reader.Read();
                    NameLabel.Text = reader["@Name"].ToString();
                    NameLabelText = NameLabel.Text;
                    reader.Close();

                    int result = (int)cmd.ExecuteScalar();
                    if (result > 0)
                    {
                        this.Hide();
                        NewsClip_Main nc_main = new NewsClip_Main();
                        nc_main.Enabled = true;
                        nc_main.ShowDialog();

                        this.Close();
                    }
                    else
                        MessageBox.Show("User Not Found!");
                    cn.Close();

推荐答案

您没有名为的参数@name 在您的SQL语句中。也许你想选择它像

You don't have a parameter called @name in your SQL statement. Perhaps you wanted to select it like

SELECT Name FROM NewsClip_Login WHERE Username = @Username AND Password = @Password";

如果您正在尝试这样做，那么您可以参考结果列wiuthout @，因为它用于参数。



关于密码的另一件事。永远不要将密码存储为纯文本。它们应始终单向散列。请查看密码存储：怎么做。 [ ^ ]



ADDITION

--------- -

If that is what you're trying to do then you refer to the result columns wiuthout @ since that is used for parameters.

Another thing concerning the password. Never ever store the passwords as plain text. They should always be hashed one-way. Have a look at Password Storage: How to do it.[^]

ADDITION
-----------

string queryText = @"SELECT Name FROM NewsClip_Login WHERE Username = @Username AND Password = @Password";

using (SqlConnection cn = new SqlConnection("Data Source=PRIMO-CHALICE;Initial Catalog=NewsClip;Integrated Security=True")) {
   using (SqlCommand cmd = new SqlCommand(queryText, cn))
   {
      cn.Open();
      cmd.Parameters.AddWithValue("@Username", UsernameTextBox.Text);
      cmd.Parameters.AddWithValue("@Password", PasswordTextBox.Text);
      SqlDataReader reader = cmd.ExecuteReader();

      reader.Read();
      NameLabel.Text = reader["Name"].ToString();
      NameLabelText = NameLabel.Text;
      reader.Close();
      ...

抱歉，我没有意识到您的SQL语句没有名称列

Sorry I didn't realize that your SQL statement not having Name column

SELECT Count(*) FROM NewsClip_Login

如果您正在使用阅读器，则应该具有列名，例如，如果您要获取值那么你应该在你的select语句中有name列。



从阅读器中删除@它应该是reader [Name]

You should have columnname if you are using reader for example if you are fetching the value of name then you should have name column in your select statement.

Remove @ from the reader it should be reader ["Name"]

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