question

Thank you very much for the detaild answer but (with all due respect) I hate copy paste I want to learn something from it. And i do not see what you have done that is not your fault but my lack of understanding C#

You created a new Class ok.....untill that I understand but than i basically get lost but again thats probably my errror I appreciate a bit more help for the sake of learning

Thanks for all the great answers I will study the example code hat will help me

I think I'm almost there but I don't understand one thing. The combobox get filled with different info as I expected and as the above example.

  //Deserialize
                     _root = HelperXml.DeserializeXMLFileToObject<XmlRoot>(ofd.FileName);
    
                     lblCompanyName.ForeColor = Color.Black;
                     lblCompanyName.Text = "Company Name: " + _root.CompanyProfile.CompanyName;
                     lblSiteName.Text ="Sitename: " + _root.CompanyProfile.SiteName;
                     lblImo.Text = "IMO: " + _root.CompanyProfile.Imo.ToString();
                     lblMachineTotal.Text = "Machine Total: " + _root.CompanyProfile.MachineTotal.ToString();
                     lblClientNumber.Text = "Clientnumber: " + _root.CompanyProfile.ClientNumber.ToString();
    
    
                     _bindingSource.DataSource = _root.MachineProfiles.ToList();
                     cmbMachineName.DataSource = _bindingSource;
                     lblPower.DataBindings.Add("Text", _bindingSource, nameof(MachineProfile.NominalPower));

This is how I have done it. I created a list of the MachineProfiles and added that to the combobox. The result is what you see in below picture I dont understand why and what I do wrong.

][2]][1]][1]][1]

With debugging I can see that the databinding from the list worked out well (I guess)

[2]: /answers/storage/attachments/213718-image.png

So I'm a bit confused cause I think I did exactly as @karenpayneoregon suggested. Does anybody see where I go wrong?

@RaymondGilbers-8810 ,Welcome to Microsoft Q&A, I used a new method to show the related information in the form.

First, I used the following code to convert the xml file to the datatable by using linq to xml.

  public DataTable GetDataTable(string file)
         {
             DataTable dt = new DataTable();
             XDocument doc = XDocument.Load(file);
             dt.Columns.Add("Imo");
             dt.Columns.Add("MachineTotal");
             dt.Columns.Add("MachineName");
             dt.Columns.Add("Type");
             dt.Columns.Add("NominalSpeed");
             dt.Columns.Add("Frequency");
             dt.Columns.Add("NominalPower");
    
             string[] arr = new string[7];
    
             var result = doc.Descendants("CompanyProfile").First();
             Console.WriteLine(result.Element("Imo").Value);
             Console.WriteLine(result.Element("MachineTotal").Value);
             var dr = from n in doc.Descendants("MachineProfile")
                      select new string[]{
                      arr[0] = result.Element("Imo").Value,
                      arr[1] = result.Element("MachineTotal").Value,
                      arr[2] = n.Element("MachineName").Value,
                      arr[3] = n.Element("Type").Value,
                      arr[4] = n.Element("NominalSpeed").Value,
                      arr[5] = n.Element("Frequency").Value,
                      arr[6] = n.Element("NominalPower").Value,
    
                  };
    
             foreach (var item in dr)
             {
                 dt.Rows.Add(item[0], item[1], item[2], item[3], item[4], item[5], item[6]);
             }
             return dt;
         }

Second, we could use combobox_SelectedValueChanged event to load the related information from the selected item.

  private void MachineNamecmb_SelectedValueChanged(object sender, EventArgs e)
         {
             DataRow row = dt.Rows.Cast<DataRow>().Where(i => i.Field<string>("MachineName") == MachineNamecmb.SelectedItem.ToString()).First();
             int index = dt.Rows.IndexOf(row);
             txtImo.Text = dt.Rows[index]["Imo"].ToString();
             txtFrequency.Text = dt.Rows[index]["Frequency"].ToString();
             txtMachineTotal.Text= dt.Rows[index]["MachineTotal"].ToString(); 
             txtType.Text= dt.Rows[index]["Type"].ToString();
             txtNominalPower.Text= dt.Rows[index]["NominalPower"].ToString();
             txtSpeed.Text = dt.Rows[index]["NominalSpeed"].ToString();
    
         }

Third, Please use the following code to load the MachineName to the combobox in the button_click event.

Result:

Best regards,
Jack

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