In the Recent Projects area next to Create: select Project.

Accept the default Project Type Visual C#: Windows, select the Template Windows Application , enter OraWinApp for the Name and enter the directory where you want the files stored in the location field (Note: if the directory does not exist, it is created). Then click OK.

The project has been created. Open the Solution Explorer view from the View menu if not already open.

Select Project > Add Reference...

Scroll down the list of References and select Oracle.DataAccess and click OK.

Click View from the menu bar and select Toolbox from the drop-down menu or put your cursor on the Toolbox to view the menu and expand Common Controls.

Select the Button control and drag it to the form canvas.

The control is shown on the canvas. You also need to create a Label.

Open the Toolbox again and drag and drop the Label control to the canvas.

Double-click the button to open the code window.

Add the C# using statements before the Public Class declaration.

using Oracle.DataAccess.Client; // ODP.NET Oracle managed provider
using Oracle.DataAccess.Types;

Add the following C# code in between the private void button1_Click(object sender, EventArgs e)
{ and } statements.

 string oradb = "Data Source=ORCL;User Id=hr;Password=hr;";

 OracleConnection conn = new OracleConnection(oradb); // C#
 conn.Open();
 
 OracleCommand cmd = new OracleCommand();
 cmd.Connection = conn;
 cmd.CommandText = "select department_name from departments where department_id = 10";
 cmd.CommandType = CommandType.Text;

 OracleDataReader dr = cmd.ExecuteReader();
 dr.Read();
 label1.Text = dr.GetString(0);

 conn.Dispose();

Select Build > Build Solution.

The project was built successfully. Now you can run the form.

Select Debug > Start Without Debugging.

The form appears. Click Button1.

The result is shown in the label. Since the query in the code was to show the department name for department id of 10, the result is the Administration department. Close Form1.

Select the Form1.cs [Design] tab. Select the Toolbox and click and drag the TextBox control to your canvas.

The textbox is shown. You can drag it to the desired location.

Select the Toolbox again and drag and drop a Label control on your canvas.

The Label is shown. Right-click Label2 and select Properties.

Change the Text to Enter Department ID:

Select the Form1.cs code tab.

You use a bind variable to include the value of the text box as part of  the SELECT statement. Bind variables improve performance by preventing the database from having to reparse the SQL statement every time the text box value changes. Add the following code right after the conn.Open()statement:

OracleParameter parm = new OracleParameter();
parm.OracleDbType = OracleDbType.Decimal;
parm.Value = textBox1.Text;

Add the cmd.Parameters statement right after the cmd.Connection statement:

cmd.Parameters.Add(parm);

Change the code for the cmd.CommandText statement to the following:

cmd.CommandText = "select department_name from departments where department_id = :1";

Select Build > Rebuild Solution.

Select Debug > Start Without Debugging.

Enter 20 for the Department ID and click Button1.

Notice that the Label1 changes to the name of the department. This value depends on what is entered in the Department ID field.

Enter 300 for the Department ID and click Button1.

This time you receive an error because there is no department with the id of 300. Click Quit. In the next topic you add some error handling so you know exactly why you received the error.

In the Form1.cs code, change the following code from:

dr.Read();
label1.Text = dr.GetString(0);

to

if (dr.Read())
{
  label1.Text = dr.GetString(0);
}
else 
{
  label1.Text = "Department ID not found";
};

Select Build > Rebuild Solution.

Select Debug > Start Without Debugging.

Enter 300 again for the Department ID and click Button1.

This time, the message Department ID is not found is displayed. Close Form1.

Click the Form1.cs [Design] tab. Select the Toolbox and drag and drop the Listbox control to the canvas.

The new listbox appears on the form. Click the Form1.cs code tab.

Delete the cmd.Parameters.Add(parm); statement.

Change the cmd.CommandText code from:

cmd.CommandText = "select department_name from departments where department_id = :1";

to

cmd.CommandText = "select department_id, department_name, city" 
                + " from departments d, locations l" 
                + " where d.location_id = l.location_id";

Also change the following lines of code from:

if (dr.Read())  
{
    label1.Text = dr.GetString(0);
}
else 
{
     label1.Text = "Department ID not found";
};

to

while (dr.Read())
{
   listBox1.Items.Add("The " + dr.GetString(1) +
                      " department is in " + dr.GetString(2));
}

Select Build > Rebuild Solution.

Select Debug > Start Without Debugging.

Click Button1.

The list of departments is shown.