c sharp windows alpplication创建登录表单 [英] c sharp windows alpplication creating login form

问题描述

hi
i我只需要2个标签和2个文本框和1个按钮

i只需在按钮中编写代码



< pre lang =cs> if （textBox1.Text！= & textBox2.Text！= ）
{
string queryText = SELECT Count（ *）FROM Login +
WHERE username = @User name AND password = @Password ;
使用（SqlConnection cn = new SqlConnection（ 数据源= MIS-PC;初始目录=项目;集成安全性=真））
使用（SqlCommand cmd = new SqlCommand（queryText，cn））
{
cn.Open（）;
cmd.Parameters.AddWithValue（ @ User name，textBox1.Text）; // cmd是SqlCommand
cmd.Parameters.AddWithValue（ @ Password，textBox2.Text）;
int result =（ int ）cmd.ExecuteScalar（）;
if （结果> 0 ）
MessageBox.Show（ Loggen In！）;
else
MessageBox.Show（ 找不到用户！）;
}

但不工作



错误这一行

int result =（int）cmd.ExecuteScalar（）;





怎么办

解决方案

你还没有提供sql连接

 sqlconnection con = new sqlconnection（）; 

请提供连接字符串，以便连接数据库，如果有任何其他问题让我知道，也请清除你的问题。

abhishek_singh是对的 - 你需要一个连接字符串连接到你的数据库，但另外...

请，请不要做那样的事情！

那里你在这里犯的两个主要错误：

1）不要连接字符串来构建SQL命令。它让您对意外或故意的SQL注入攻击持开放态度，这可能会破坏您的整个数据库。请改用参数化查询。正如您的代码所代表的那样，我不需要密码即可以任何人身份登录！

2）绝不以明文形式存储密码 - 这是一个主要的安全风险。有关如何在此处执行此操作的信息：密码存储：如何做到这一点。 [ ^ ]

在两个地方用@Username替换@User名称，然后再次运行该代码。

hi i just i take 2 lables and 2 textboxes and 1 button
i just write the code in button

if (textBox1.Text != "" & textBox2.Text != "")
           {
               string queryText = "SELECT Count(*) FROM Login " +
                                  "WHERE username = @User name AND password = @Password";
               using (SqlConnection cn = new SqlConnection("Data Source=MIS-PC;Initial Catalog=project;Integrated Security=True"))
               using (SqlCommand cmd = new SqlCommand(queryText, cn))
               {
                   cn.Open();
                   cmd.Parameters.AddWithValue("@User name", textBox1.Text);  // cmd is SqlCommand
                   cmd.Parameters.AddWithValue("@Password", textBox2.Text);
                   int result = (int)cmd.ExecuteScalar();
                   if (result > 0)
                       MessageBox.Show("Loggen In!");
                   else
                       MessageBox.Show("User Not Found!");
               }

but its not working

Error in this line
int result = (int)cmd.ExecuteScalar();


how to do

解决方案

you have not provided sql connection in to

sqlconnection con=new sqlconnection();

please provide connection string on that so that connect with database, if any other issue let me know about that, also please clear your question.

abhishek_singh is right - you need a connection string to connect to your db, but in addition...
Please, please, don't do things like that!
There are two major mistakes you are making here:
1) Do not concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Use Parametrized queries instead. As your code stands, I do not need a password to log in as anybody!
2) Never store passwords in clear text - it is a major security risk. There is some information on how to do it here: Password Storage: How to do it.[^]

replace @User name with @Username on both place, then again run that code.

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