使用c＃不更新MSAccess数据库更新

Question

I am making a database system. I've implemented the INSERT function properly but when I tried implementing the UPDATE function, I couldn't make any changes to the database. I don;t know where I went wrong.
Note: username is declared as string

Here is the function handling the UPDATE:

private void btnUpdate_Click(object sender, EventArgs e)
    {

        string q = "UPDATE [registrationinfo] SET [Password]='?', [EmailAdd]='?', [HomeAdd]='?' WHERE [Username]='?'";

        OleDbConnection connect = new OleDbConnection(MyConnectionString);
        connect.Open();
        try
        {
            OleDbCommand command = new OleDbCommand(q,connect);

            command.Parameters.AddWithValue("@Password", txt_password.Text);
            command.Parameters.AddWithValue("@EmailAdd", txt_eadd.Text);
            command.Parameters.AddWithValue("@HomeAdd", txt_homeadd.Text);
            command.Parameters.AddWithValue("Username", username);

            command.ExecuteNonQuery();

            txt_password.Clear();
            txt_eadd.Clear();
            txt_homeadd.Clear();
            txt_conPass.Clear();
        }
        catch (Exception ex)
        {
            connect.Close();
            MessageBox.Show(ex.Message.ToString());
        }

        connect.Close();            
    }

Answer 1

当使用参数化查询，你不需要把单引号（ ' ）将文本参数在你的CommandText，所以你应该使用这样的：

string q = "UPDATE [registrationinfo] SET [Password]=?, [EmailAdd]=?, [HomeAdd]=? WHERE [Username]=?";