ExecuteReader();不行

问题描述

我希望搜索数据库是表中存在的用户.然后我写这个.但是用黄色标记"SqlDataReader reder = cmd.ExecuteReader();"不能做我的工作吗?
这是问题吗abt"ExecuteReader()" ??????

帮我

I want search database is user existing in the table.then i write this. but mark " SqlDataReader reder = cmd.ExecuteReader();" in yellow color and cant do my work?
is this problem abt" ExecuteReader()"???

help me

SqlConnection con = new SqlConnection("Data Source=thushan-pc;Initial Catalog=dvd;Integrated Security=True");
bool b=false;
SqlCommand cmd=new SqlCommand("select User_Name from users where=(''"+txtop.Text+"'')",con);
con.Open();

SqlDataReader reder = cmd.ExecuteReader();
if (reder.Read() == true)
b = true;
reder.Close();
cmd.Dispose();

con.Close();
if (b == true)
MessageBox.Show("User here");

推荐答案

select User_Name from users where=(''John'')

现在尝试使其成为合法的Sql select语句:

Now try making it a legitimate Sql select statement:

SELECT User_Name FROM users WHERE User_Name=''John''

(我将大写的SQL语法词大写，使其更易于解密-值得一提).

如果您将此操作作为参数化查询，则不需要引号，或者...

[edit]手指麻烦:"AddWithValue"中没有"Q"-OriginalGriff [/edit]

(I have capitalised SQL syntax words to make it easier to decipher - worth doing as a general rule).

If you do this as a parameterized query, you won''t need the quotes, either...

[edit]Finger trouble: there is no "Q" in "AddWithValue" - OriginalGriff[/edit]

using(SqlConnection con = new SqlConnection("Data Source=thushan-pc;Initial Catalog=dvd;Integrated Security=True"))
{
bool b=false;
using(SqlCommand cmd=new SqlCommand("select Count(User_Name) from users where UserName=''"+txtop.Text+"''",con))
{
  con.Open();

   SqlDataReader reder = cmd.ExecuteReader();
  if (reder.Read())
     if(Convert.ToInt32(dr[0]) == 1)
  {
     b = true;
     break;
  }
reder.Close();
cmd.Dispose();
}
con.Close();
if (b == true)
MessageBox.Show("User here");
}

使用Count而不是仅依赖reder.Read()是一个好习惯.我希望这能帮到您. :rose:

It is a good practice to use Count rather than only to rely on reder.Read(). I hope this will help you. :rose:

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