如何从表的一列相对于表的另一列获取价值? [英] How to get value from one column of a table with respect to other column of a table?

问题描述

我的SQL数据库中有两个列.一种是用户名，另一种是ID.如果我在第一个文本框中输入ID，则第二个文本框中可以显示相应的用户名.请帮助我.

Hi,
I have two colomns in my sql database. One is username and other one column for ID. If i give id in first text box, the second text box can show the corresponding username. Kindly help me.

Private void lblGET_Click(object sender, EventArgs e)
{
   SqlDataAdapter da = new SqlDataAdapter("select username from login where Answer='"+txtFCN.Text+"'",con);
   dt = new DataTable();
   da.Fill(dt);
   if (dt.Rows.Count != 0)
   { lblANSUN.Text = dt.Rows.Count.ToString();
   }
}

我正在使用此代码...但是它仅显示行数..请清除我的疑问.

谢谢，

Viswanathan.M

I am using this code...but it shows only number of rows..please clear my doubt.

Thanks,

Viswanathan.M

推荐答案

这是不好的方法，因为它允许进行sql注入.您需要限制文本框值的长度，并确保它不是讨厌的，即仅包含数字值.

This is the bad approach as it allows for sql injection. You would need to limit the length of the textbox value and also make sure it is not a nasty i.e. only contains a numeric value.

String sqlcmd = "Select Username from theTable where ID='" + textbox.text + "'";

最好的方法是使用参数；
参见本文(但也有许多其他文章)； C#和表值参数 [

The best way is to use parameters;
See this article (but there are many others also); C# and Table Value Parameters[^]

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