combobox value pass as a parameter

Kristine Legzdiņa

user select first combobox value, then select second combobox value. Then when he precc Button i need to pass these double type values to method as a parameters.

im new in c# and this is part of home work. I need to create delegate.

part of code looks like:

i create delegate.

public delegate double operation(double x, double y);

i create class with one simple method.

public class Program

{

internal static double Addition(double a, double b)

{

return a + b;

}

then i create object

operation obj = new operation(Program.Addition);

textBox1.Text = (obj( comboxox1Value, comboxox2Value));

for now it seems to me, i will never become a programmer...

9 Replies

Know the answer? Post it — somebody with the same question will find it here.

Nitin Sontakke8y ago
Accepted answer
You didn't mention how you have populated comboboxes.

Try following, assuming everything else is correct and you have populated comboboxes with value double values:

TextBox1.Text = obj(Double.Parse(ComboBox1.SelectedText), Double(ComboBox2.SelectedText));

Try not to give up this early. However, let me add this. You definitely need quite a different type of attitude towards problem solving. A different kind of way of thinking. A great amount of perseverse and persistance.

Trust me, it is almost certainly not at all difficult. It's just different.

There are patterns, which you should be able to pick-up really quickly to learn faster. Once these patterns are understood rest all is very easy.

One more thing, just concentrate on understanding WHYs, then HOWs will not sound difficult to you.
Kristine Legzdiņa8y ago
i want to say big thanks for helping me! My trivial delegate works! and code looks like this:
private void button2_Click(object sender, EventArgs e)
{
if ((cb_OLSF_L.Text == "") || (cb_OCLY_L.Text == ""))
{
// MessageBox.Show("seit strings");
}
else
{
double lsf = (double)Convert.ToDouble(cb_OLSF_L.Text);
double lcly = (double)Convert.ToDouble(cb_OCLY_L.Text);
operation obj = new operation(Program.Addition);
double sagllsf = obj(lsf, lcly);
txt_sf_p.Text = sagllsf.ToString();
}
}
Nitin Sontakke8y ago
I am not too sure, if you understand or not but the error has now progressed further.

Your operation is returning a double and you are trying to assign it to the Text property of a TextBox, which is of data type String, hence the error, if you read carefully.

Try modifying as follows:
txt_sf_p.Text = obj(double.Parse(cb_OLSF_L.SelectedText), Double.Parse(cb_OCLY_L.SelectedText).ToString()
The best approach, actually, is to assign a result to a double variable and then assign it to text box as shown below:
Double result = obj(double.Parse(cb_OLSF_L.SelectedText), Double.Parse(cb_OCLY_L.SelectedText);
txt_sf_p.Text = result.ToString();
And going a step even further, you should even assign parameter values also first to some double variables and then pass those variables to the operation. This way your code becomes lengthy, but initially this is okay. As you become experienced, you can skip all those additional steps altogether.
Hope you get what I am trying to convey. Goodluck!
Kristine Legzdiņa8y ago
ok, i found that problem was because i want send double to textbox. so now i need to finde out how to double value sent to textbox.
Kristine Legzdiņa8y ago
to Nitin Sontakke :

of course, i try to add .Parse too. Same error.
Kristine Legzdiņa8y ago
Rafnas T P : nop, i still have an error.
Nitin Sontakke8y ago
If you notice, I forgot to type .Parse for the second dropdown box value. Just add that. See how first parameter is passed, second should be similar.
Rafnas T P8y ago
hi,
try below one
txt_sf_p.Text = obj(Convert.ToDouble(cb_OLSF_L.SelectedText), Convert.ToDouble(cb_OCLY_L.SelectedText));
Kristine Legzdiņa8y ago
Thank You for Your suggestion!

well, i still have an error. There is underlined second parameter.

About combobox usage - first homework was to create database. Then i created code, so i can store in database combobox values- it wasnt so difficult like I now struggle.

Then for now, homework is to upgrade programm with one delegate. So i decided to use again combobox values.

Code in this form looks like this:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.OleDb;
namespace WindowsFormsApplication3
{
public partial class Main : Form
{
private OleDbConnection cone = new OleDbConnection();
private void Main_Load(object sender, EventArgs e)
{
}
public void btn_saglabat_Click(object sender, EventArgs e)
{
try
{
cone.Open();
OleDbCommand command = new OleDbCommand();
command.Connection = cone;
command.CommandText = "insert into kl_info(lsf, lcly, lass, ladd, ksf, kcly, kass, kadd, klvards, kluzvards, kltel) values(@lsf, @lcly, @lass, @ladd, @ksf, @kcly, @kass, @kadd, @klvards, @kluzvards, @kltel)";
command.Parameters.AddWithValue("lsf", cb_OLSF_L.GetItemText(cb_OLSF_L.SelectedItem));
command.Parameters.AddWithValue("lcly", cb_OCLY_L.GetItemText(cb_OCLY_L.SelectedItem));
command.Parameters.AddWithValue("lass", cb_OASS_L.GetItemText(cb_OASS_L.SelectedItem));
command.Parameters.AddWithValue("ladd", cb_OADD_L.GetItemText(cb_OADD_L.SelectedItem));
command.Parameters.AddWithValue("ksf", cb_OSF_K.GetItemText(cb_OSF_K.SelectedItem));
command.Parameters.AddWithValue("kcly", cb_OCLY_K.GetItemText(cb_OCLY_K.SelectedItem));
command.Parameters.AddWithValue("kass", cb_OASS_K.GetItemText(cb_OASS_K.SelectedItem));
command.Parameters.AddWithValue("kadd", cb_OADD_K.GetItemText(cb_OADD_K.SelectedItem));
command.Parameters.AddWithValue("klvards", txt_vards.Text);
command.Parameters.AddWithValue("kluzvards", txt_uzvards.Text);
command.Parameters.AddWithValue("kltel", txt_tel.Text);
command.ExecuteNonQuery();
MessageBox.Show("Dati saglabati");
cone.Close();
}
catch (Exception ex)
{
MessageBox.Show("Error" + ex);
}
}
private void btn_loaddb_Click(object sender, EventArgs e)
{
try
{
cone.Open();
OleDbCommand cmndd = new OleDbCommand();
cmndd.Connection = cone;
string dbmainig = "Select id, lsf, lcly, lass, ladd, ksf, kcly, kass, kadd, klvards, kluzvards, kltel from kl_info";
cmndd.CommandText = dbmainig;
OleDbDataAdapter dapt = new OleDbDataAdapter(cmndd);
DataTable dtbl = new DataTable();
dapt.Fill(dtbl);
dataGridView1.DataSource = dtbl;
cone.Close();
}catch (Exception ex)
{
MessageBox.Show("Error" + ex);
}
}
private void btn_aizvert_klLogs_Click(object sender, EventArgs e)
{
this.Close();
}
private void button1_Click(object sender, EventArgs e)
{
RedzesSpecialists redzesSp = new RedzesSpecialists();
redzesSp.Show();
}
private void textBox6_TextChanged(object sender, EventArgs e)
{
}
public delegate double operation(double x, double y);
public class Program
{
internal static double Addition(double a, double b)
{
return a + b;
}
}
private void button2_Click(object sender, EventArgs e)
{
operation obj = new operation(Program.Addition);
txt_sf_p.Text = obj(double.Parse(cb_OLSF_L.SelectedText), Double(cb_OCLY_L.SelectedText));
}
public Main()
{
InitializeComponent();
cone.ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source='C:\md data base\login_info.mdb'";
}
}
}