问从MySQL db检索数据

EN

String^ constring = L"datasource=localhost; port=3306; username=root; password="; /
MySqlConnection^ conDB = gcnew MySqlConnection(constring); 
MySqlCommand^ Query = gcnew MySqlCommand("SELECT Bar FROM utilizadores.users  WHERE username='"+user+ "' ", conDB ); 
MySqlDataReader^ reader;
onDB->Open();

double^ bar_value;
String^ messagebox_bar_values;
try 
{
    reader = Query->ExecuteReader(); 
while (reader->Read())
{
    bar_value=reader->GetDouble(1);
    messagebox_bar_values=messagebox_bar_values+bar_value.ToString + ",";

    //Alternatively the line below should also work. If we are not concerned about the datatype and read the value directly as a string.
    //Just comment out the two lines above
    //messagebox_bar_values=messagebox_bar_values+reader["Bar"]->ToString;

}
    MessageBox::Show(messagebox_bar_values);
}
catch (Exception^ex)
{
    MessageBox::Show(ex->Message); 
}

reader = Query->ExecuteReader(); 

String bar = "Bar not found for the user '" & user & "'"

if( reader.Read() ) ' hope the statement returns a single row, and hence `if`
  bar = reader.GetString( 0 )
end if

reader.close()

MessageBox::Show( bar );