C# 表单未将值插入 SQL Server 数据库

问题描述

我有一个简单的创建一个新用户表单，它从两个文本框中获取值，用户名和密码.button2 单击事件应采用这些值并将它们插入到数据库中的用户表中.但是，当我运行我的代码时，会出现消息框说数据已添加，我无法使用 VS2010 看到数据库中的数据.

I have a simple create a new user form which takes values from two text boxes, username and password. The button2 click event should take these values and insert them into the Users table in the database. However, when I run my code the message box appears to say the data has been added, I cannot see the data in the database using VS2010.

查看 VS 中数据库连接的屏幕截图.我还在 VS 中创建了数据库的数据源.

See screen shot for the database connection in VS. I have also created a datasource of the database in VS.

有什么想法吗?

非常感谢.

private void button2_Click(object sender, EventArgs e)
    {
        string username = txtUsername.Text;
        string password = txtPassword.Text;
        string sqlquery;
        string connection = @"Data Source=.SQLEXPRESS;AttachDbFilename='C:UsersNickDocumentsVisual Studio 2010ProjectsDebenhamsProjectOffice V.01DebenhamsProjectOffice V.01DebenhamsProjectOfficeDatabase.mdf';Integrated Security=True;Connect Timeout=30;User Instance=True";
        SqlConnection cn = new SqlConnection(connection);
        try
        {
            cn.Open();
        }
        catch (Exception)
        {
            MessageBox.Show("Unable to connect to Database");
        }

        sqlquery = "INSERT INTO Users (Username, Password) VALUES ('" + txtUsername.Text + "','" + txtPassword.Text + "')";
        try
        {
            SqlCommand command = new SqlCommand(sqlquery, cn);
            command.Parameters.AddWithValue("Username", username);
            command.Parameters.AddWithValue("Password", password);
            command.Parameters.Clear();
            MessageBox.Show("User Added");
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
        txtUsername.Text = "";
        txtPassword.Text = "";
        cn.Close();
    }

推荐答案

只是尝试修复代码.有些元素很重要，有些元素只是优雅.试试看，它可能会起作用.或者可以指出错误所在:

Just trying a code fix. Some elements are crucial, some are just elegant. Try it, it might work., or could point to where the error is:

private void button2_Click(object sender, EventArgs e)
    {
        string username = txtUsername.Text;
        string password = txtPassword.Text;
        string sqlquery;

        //Put away the apostrophes and used twice double quotations for
        //the full path of the database file:
        string connection = @"Data Source=.SQLEXPRESS;AttachDbFilename=""C:UsersNickDocumentsVisual Studio 2010ProjectsDebenhamsProjectOffice V.01DebenhamsProjectOffice V.01DebenhamsProjectOfficeDatabase.mdf"";Integrated Security=True;Connect Timeout=30;User Instance=True";
        SqlConnection cn = new SqlConnection(connection);

        /* Better to let the program fail than think it's open and moving on
        removed try, catch*/
        cn.Open();


        //Why using your TextBoxes values if you already created strings?
        //changed

        //you should also be careful users can't type something like "') in the      
        //textboxes or they may cause a SQL injection

        sqlquery = "INSERT INTO Users (Username, Password) VALUES ('" + username + "','" + password + "')";

        try
        {
            SqlCommand command = new SqlCommand(sqlquery, cn);
            /* unnecessary since you already built a query command.Parameters.AddWithValue("Username", username);
            command.Parameters.AddWithValue("Password", password);
            command.Parameters.Clear();   */

            //Missing!!
            command.ExecuteNonQuery();
            MessageBox.Show("User Added");
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }

        //Elegance
        txtUsername.Clear();
        txtPassword.Clear();
        cn.Close();
    }

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