[英]how to insert , delete , select records into database using datagridview cells and datagridview events using c#?
[英]How to insert,delete,select,update values in datagridview in C# using MYSQL
下面是使用datagridview将值插入mysql数据库的代码。 但是selectcommand是有效的。它不会发生,因为我收到错误消息,指出“列'username'不能为null”。
如果我使用ms Access数据库,则不会弹出此错误。 谁可以帮我这个事。 还有其他方法可以这样做。
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);
}
我不太确定,但是mysql是否不使用带有“?”-synatx的编号参数或带有“:”-syntax而不是(mssql)at-syntax的命名参数?
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");
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");
在使用datagrid(vb.net)在mysql中更新时遇到了类似的问题。 解决了:
Dim cmb As New MySqlCommandBuilder(datGrid)
Me.datGrid.Update(datSet, "mysqlTableToUpdate")
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