How Do I Use Class For Ojects In A Form

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Dear All,

I had got multi forms with a common combo box object in many forms, which contains session/financial year. What I'm doing right now is writing again and again same code for the combo object.

Now, what I need is a class where I just write the code and can access for combo box on any form by referring to that class.

And I donno how to do that...

efforts I did : GOOGLE for this and tried by myself by creating a class and wrote code in it but couldn't achieve the target.

code:

C#

class financial_session
    {
        connectionString cs = new connectionString();
            
                OleDbConnection database = new OleDbConnection(cs.connString());
                database.Open();

                string queryString = "Select distinct(bc_session) from cm_master order by bc_session desc";

                OleDbCommand cmd = new OleDbCommand(queryString, database);
                OleDbDataReader dr = cmd.ExecuteReader();

                cmbSession.Items.Clear();

                while (dr.Read())
                {
                    cmbSession.Items.Add(dr.GetValue(0).ToString());
                }
                database.Close();

    }

Posted 30-Jul-14 22:04pm

sachees123

Updated 30-Jul-14 22:08pm

CPallini

v2

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2 solutions

Solution 2

Create a UserControl, and either derive it from ComboBox or embed a ComboBox in it.
Add your code to that class, and use the next control instead of the "raw" ComboBox in all your forms.

It's easier than it sounds - I do it all the time, even if I will only be using the control once (since it encapsulates the control functions, and simplifies the form code significantly).
MSDN[^] can help with the details.

Posted 30-Jul-14 22:33pm

OriginalGriff

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Sharmanuj · Accepted Answer · 2014-07-30T22:32:00

Solution 1

Make a class and create a method to bind data into combo box control.

Here is the sample code to bind the combobox control.

C#

public void BindComboBoxDataContext(ComboBox comboBox, DataTable dtDataContext, string displayMemberPath, string selectedValueMemberPath)
        {
            try
            {
                comboBox.DataContext = dtDataContext;
                comboBox.DisplayMemberPath = displayMemberPath;
                comboBox.SelectedValuePath = selectedValueMemberPath;
                comboBox.SelectedIndex = -1;
            }
            catch (Exception ex)
            { LogExceptionDetails(ex); }
        }

Whenever required to set the data for the control, just make an object for this class and call this method.

Posted 30-Jul-14 22:32pm

Sharmanuj

Comments

sachees123 31-Jul-14 6:36am

thanks for your prompt reply, im getting an error

Error 3 Expected class, delegate, enum, interface, or struct

Sharmanuj 31-Jul-14 6:44am

This is the method provided which you have to embed into a class. Then use on your forms.

Sharmanuj 31-Jul-14 6:46am

you have to include the required namespaces as well on the class which you'll prepare.

sachees123 31-Jul-14 6:46am

I did the same , here is the code, plz tell me where i'm doing wrong

using System;
using System.Collections.Generic;
using System.Text;

namespace MINE.classes
{
class bc_session
{
}
public void BindComboBoxDataContext(ComboBox comboBox, DataTable dtDataContext, string displayMemberPath, string selectedValueMemberPath)
{
try
{
comboBox.DataContext = dtDataContext;
comboBox.DisplayMemberPath = displayMemberPath;
comboBox.SelectedValuePath = selectedValueMemberPath;
comboBox.SelectedIndex = -1;
}
catch (Exception ex)
{ }
}
}

Sharmanuj 31-Jul-14 6:47am

Try This code

using System;
using System.Collections.Generic;
using System.Text;

namespace MINE.classes
{
class bc_session
{

public void BindComboBoxDataContext(ComboBox comboBox, DataTable dtDataContext, string displayMemberPath, string selectedValueMemberPath)
{
try
{
comboBox.DataContext = dtDataContext;
comboBox.DisplayMemberPath = displayMemberPath;
comboBox.SelectedValuePath = selectedValueMemberPath;
comboBox.SelectedIndex = -1;
}
catch (Exception ex)
{ }
}
}
}

sachees123 31-Jul-14 7:01am

I did this too, now the error is

Error 1 The type or namespace name 'ComboBox' could not be found (are you missing a using directive or an assembly reference?)

Sharmanuj 31-Jul-14 7:23am

Right click on the ComboBox and resolve it. That will include the namespace in your current class.

sachees123 31-Jul-14 7:36am

Thank, it resolve namespace problem,

now, I'm using this method in my form, where I defined first two values but not get the value for string displayMemberPath, string selectedValueMemberPath

Sharmanuj 31-Jul-14 8:04am

For ComboBox controls we have 2 basic values
a. Id and b. Text

In the same manner DisplayMemberPath is the Text Value and SelectedValueMemberPath would be ID.

you can pass same values in both the parameters if required. but the best practice is to bind with ID and Text.

sachees123 31-Jul-14 8:25am

System.Data.DataViewManagerListItemTypeDescriptor

This is the outcome of the above efforts by us in combo box.

here I escape the last two values of method given by you

Sharmanuj 1-Aug-14 0:34am

Could you post your code here in which you are getting error

sachees123 1-Aug-14 1:08am

Sure, I will but now let me try to solve it first... the time I will give up will give code...

sachees123 1-Aug-14 3:01am

string queryString = "Select distinct(bc_session) from cm_master order by bc_session desc";
OleDbDataAdapter da = new OleDbDataAdapter(queryString, cs.connString());
DataSet ds = new DataSet();
DataTable dt = new DataTable();
da.Fill(dt);

BC.BindComboBoxDataContext(cmbSession, da);

Sharmanuj 1-Aug-14 3:05am

add a new parameter in the method as fieldName and pass the value as provided below.

BC.BindComboBoxDataContext(cmbSession, dt, dt.Columns[0].ToString());

Sharmanuj 1-Aug-14 3:07am

Pass the Datatable to bind the value. you are passing DataAdapter object in method.

sachees123 1-Aug-14 3:16am

yupeeee....got the result .. thanks a ton..
but some correction that I did in class

internal void BindComboBoxDataContext(System.Windows.Forms.ComboBox cmbSession, DataTable dt, string p)
{
try
{
cmbSession.DataSource = dt;
cmbSession.SelectedIndex = -1;
cmbSession.DisplayMember = p;
}
catch (Exception ex)
{ }
}

what you had given is control type and it required form type of comboBox. So now my question is when we can use control type objects?

Sharmanuj 1-Aug-14 3:30am

kindly explain you question

sachees123 1-Aug-14 4:08am

this is the error I get while compiling
Error 24 Argument 1: cannot convert from 'System.Windows.Forms.ComboBox' to 'System.Windows.Controls.ComboBox'

when my method is
public void BindComboBoxDataContext1(ComboBox comboBox, DataTable dtDataContext, string displayMemberPath)

now what is did is change method to:
internal void BindComboBoxDataContext(System.Windows.Forms.ComboBox cmbSession, DataTable dt, string p)

and it works. I hope you got my point/question

Sharmanuj 1-Aug-14 4:22am

See that is based on the application format. I gave you the example for WPF application in which ComboBox class is under namespace "System.Windows.Controls".
The same ComboBox class exists in Winfroms under namespace "System.Windows.Forms".

I hope this is clear to you.

sachees123 1-Aug-14 4:37am

Ok, thanks once again