如何使用MYSQL在C＃中的datagridview中插入，删除，选择，更新值 [英] How to insert,delete,select,update values in datagridview in C# using MYSQL

问题描述

下面是使用datagridview将值插入到mysql数据库中的代码。
但是selectcommand正在工作。它不会发生，因为我收到错误说明列用户名不能为空。

Below is the code to insert value into mysql database, using datagridview. But the selectcommand is working.It is not happening since i get error stating "Column 'username' cannot be null ".

如果我使用ms访问数据库，则不会弹出此错误。
任何人都可以帮助我。有没有其他方法可以这样做。

This error does not pop up if i use ms access database. Can anyone help me on this. is there any other method to do so.

private void button1_Click(object sender, EventArgs e)
    {    //Even using functions we can easily update the datagridview
        //Select_function();

        try
        {   //The container which displays the details.
            dataGridView1.Visible = true;

            //The binding object which binds the datagridview with backend.
            BindingSource bs = new BindingSource();

            //The datatable through which data is exported to datagridview
            table = new DataTable();
            bs.DataSource = table;
            this.dataGridView1.DataSource = bs;

            MySqlConnection conn = new MySqlConnection(db);
            conn.Open();

            string s = "select *from user";
            cmd = new MySqlCommand(s, conn);

            da = new MySqlDataAdapter();
            da.SelectCommand = new MySqlCommand(s, conn);

            //There is issue in below sytax of insert command.
            MySqlCommand insertcommand = new MySqlCommand("insert into user(username,password) values(@username ,@password)", conn);
            insertcommand.Parameters.Add("username",MySqlDbType.VarChar,50,"username");
            insertcommand.Parameters.Add("password", MySqlDbType.VarChar, 50, "password");
            da.InsertCommand = insertcommand;


            //Demonstrates update command
            MySqlCommand updatecommand = new MySqlCommand("update user set username=@username,password=@password where (username=@username)", conn);
            updatecommand.Parameters.Add("@username", MySqlDbType.VarChar, 50, "username");
            updatecommand.Parameters.Add("@password", MySqlDbType.VarChar, 50, "password");

             da.UpdateCommand = updatecommand;



            //Demonstration of delete Command
            MySqlCommand deletecommand = new MySqlCommand("delete from user where username=@username", conn);
            deletecommand.Parameters.Add("@username", MySqlDbType.VarChar, 50, "username");
            da.DeleteCommand = deletecommand;

            da.Fill(table);
            conn.Close();

        }
        catch (Exception err) { MessageBox.Show(err.Message); } 

    }
    private void button2_Click(object sender, EventArgs e)
    {  da.Update(table);
    }

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推荐答案

我是相当不确定，但是mysql是否使用带有？的编号参数 - synatx或带有：语法的命名参数，而不是（mssql）语法？

I am rather unsure, but doesn't mysql use numbered parameters with a "?"-synatx or named parameters with a ":"-syntax instead of (mssql) at-syntax ?

某些东西：

MySqlCommand insertcommand = new MySqlCommand("insert into user(username,password) values(?, ?)", conn);
insertcommand.Parameters.Add(1, MySqlDbType.VarChar,50,"username");
insertcommand.Parameters.Add(2, MySqlDbType.VarChar, 50, "password");

或

MySqlCommand insertcommand = new MySqlCommand("insert into user(username,password) values(:username, :pass)", conn);
insertcommand.Parameters.Add(":username", MySqlDbType.VarChar,50,"username");
insertcommand.Parameters.Add(":pass", MySqlDbType.VarChar, 50, "password");

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