Login code need help please

Question

1.00/5 (1 vote)

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i need some help

C#

protected void btnLogin_Click(object sender, EventArgs e)
        {
            string query = "Select Count(*) From LoginInfo Where lo_name = @username And lo_password = @password";
            int userId = 0;
            using (SqlConnection conn = new SqlConnection(conStr))
            {
                using (SqlCommand cmd = new SqlCommand(query, conn))
                {
                    cmd.CommandType = CommandType.Text;
                    cmd.Parameters.AddWithValue("@username", txtUsername.Text);
                    cmd.Parameters.AddWithValue("@password", txtPassword.Text);
                    cmd.Connection = conn;
                    conn.Open();
                    userId = Convert.ToInt32(cmd.ExecuteScalar());
                    conn.Close();
                }
                if(userId>0)
                {
                    Response.Redirect("Default.aspx");
                }
                else
                {
                    lable1.Text = "Login Fialed";
                }
            }
            
        }

when i clicked on login button it give error on the following codes

C#

userId = Convert.ToInt32(cmd.ExecuteScalar());

Posted 18-Aug-15 19:56pm

Altaful Haq

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Comments

Patrice T 19-Aug-15 2:13am

Which error message ?

3 solutions

Solution 1

C#

object objValue = cmd.ExecuteScaler();
if (objValue != DbNull.Value)
{
  userId = Convert.ToInt32(objValue);
}

Posted 18-Aug-15 20:12pm

DamithSL

Solution 2

Try:

userId = (int) cmd.ExecuteScalar();

But please, don't store passwords in plain text!
See here: Password Storage: How to do it.[^]

Posted 18-Aug-15 20:15pm

OriginalGriff

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Sergey Alexandrovich Kryukov · Accepted Answer · 2015-08-18T20:18:00

Don't use convert, use (int)cmd.ExecuteScalar(); https://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.executescalar%28v=vs.110%29.aspx[^].

Make sure your table data type is really integer. In worse case, do dynamic cast to test it:

C#

int value = cmd.ExecuteScalar() as int;
if (value != null)
   // do something
else
   // indicate that something goes wrong,
   // for example, throw more informative exception
   // then the cast exception

By the way, Convert is rarely useful. For example, if the object is string (compile-time type), better use parse methods, such as int.Parse or int.TryParse.

—SA