登录代码需要帮助 [英] Login code need help please

问题描述

我需要一些帮助

i need some help

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";
                }
            }
            
        }

当我点击登录按钮时，它会对以下代码给出错误

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

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

推荐答案

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

尝试：

Try:

userId = (int) cmd.ExecuteScalar();

但请不要以明文形式存储密码！

见这里：密码存储：怎么做。 [ ^ ]

不要使用convert，使用（int）cmd.ExecuteScalar（）; https://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.executescalar%28v= vs.110％29.aspx [ ^ ]。



确保您的表数据类型确实是整数。在更糟糕的情况下，做动态转换来测试它：

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:

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

顺便说一句，转换很少有用。例如，如果对象是字符串（编译时类型），最好使用解析方法，例如 int.Parse 或 int.TryParse 。

-SA

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

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