如何使用MYSQL在C＃中的datagridview中插入，删除，选择，更新值

下面是使用datagridview将值插入mysql数据库的代码。 但是selectcommand正在工作。它没有发生，因为我收到错误声明“列’用户名’不能为空”。

如果我使用ms访问数据库，则不会弹出此错误。 谁可以帮我这个事。 有没有其他方法可以这样做。

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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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Answer 1

我不太确定，但不是mysql使用编号参数和“？” – synatx或带有“：”的命名参数 – 语法而不是（mssql）at-syntax？

就像是 ：

 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"); 

要么

 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"); 

Answer 2

我认为您需要更改添加到insert命令的参数的名称以匹配INSERT SQL语句中指定的名称。

尝试：

 insertcommand.Parameters.Add("@username",MySqlDbType.VarChar,50,"username"); insertcommand.Parameters.Add("@password", MySqlDbType.VarChar, 50, "password"); 

Answer 3

用datagrid（vb.net）在mysql中更新类似的问题。 解决了它：

 Dim cmb As New MySqlCommandBuilder(datGrid) Me.datGrid.Update(datSet, "mysqlTableToUpdate")