Make Phone Call in .NET

 

“Making a phone call with a .NET application was THAT simple? And I always thought [that] only a real savvy can do such a state-of-the-art work.”

 

were the comments given by a friend of mine when I showed him this demo project. But the truth is; that this task was never so easy until a real savant made it easy as pie for all of us. Thanks to Julmar Technology ( http://www.julmar.com/ ).

 

These folks have done a magnificent work and provided us with a class library built upon TAPI 2.x (distributed with Windows XP). TAPI, so far does not give any interface which can be used in .NET to make a phone call. Nonetheless, with the class library we have in our hand now, making a phone call is as easy as instantiating an object and calling its appropriate functions. So let’s see the magic.

 

Creation of Phone Caller Application:

The main logic behind this application is; we want to display a simple Listbox with a few persons’ information populated in it. Each person will have an ID, Name, Phone Number etc. When user selects a person in the list it will show person’s information in the textboxes present on the form. Phone Number textbox has a button in front of it. Clicking this button will initiate a phone call. Let’s quickly take a look at how this form is going to look like:

So we’ll create a simple windows application and add references to our DLL file which gives our application the ability to make phone calls.

 

·        Start Microsoft Visual Studio 2003 or later.

·        Click Create New Project

·        In New Project dialog box, select Visual C# in Project types panel on left.

·        Select Windows Forms Application in the Templates panel on right.

Give a decent physical path and name to your project and select OK.

 

By doing this, IDE will create a windows application project with a default form added into it.

 

·        Rename your Form1.cs to frmPersons.cs

·        Next step we need Atapi.dll; the heart of this application

·        Atapi.dll can be found here http://www.julmar.com/tapi/atapinet.zip

·        Unzip this file and reach bin folder and get the dll.

·        Add a reference to Atapi.dll by right clicking project root node in Solution Explorer

·        Add app.config

 

After completing the above steps your Solution Explorer should look something like this:

 

We also want to keep a complete log of TapiManager’s activities; app.config keeps the path of the log file.   

 

<appSettings>

            <add key=“LogFilePath“ value=“D:\My Work\prjMakePhoneCall\PhoneCall.log“/>

</appSettings>

 

Now let’s move to cs code of frmPersons.cs; namespaces first here:

 

 

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

using System.IO;

using System.Configuration;

using JulMar.Atapi;

 

And then comes the rest of the code:

 

I’ve created a small class of Person. This class contains some private data members and their corresponding public properties, followed by 2 overloaded constructors. That’s how the class looks like, and I’ve written the class within frmPersons.cs itself:

 

    [Serializable]

    public class Person

    {

        private int id;

        private string name;

        private string phone;

        private string city;

        private string state;

        private string zip;

        private string country;

 

        public int ID

        {

            get { return id; }

            set { id = value; }

        }

        public string Name

        {

            get { return name; }

            set { name = value; }

        }

        public string Phone

        {

            get { return phone; }

            set { phone = value; }

        }

        public string City

        {

            get { return city; }

            set { city = value; }

        }

        public string State

        {

            get { return state; }

            set { state = value; }

        }

        public string Zip

        {

            get { return zip; }

            set { zip = value; }

        }

        public string Country

        {

            get { return country; }

            set { country = value; }

        }

 

        public Person()

        {

 

        }

        public Person(int id, string name, string phone, string city, string state, string zip, string country)

        {

            this.id = id;

            this.name = name;

            this.phone = phone;

            this.city = city;

            this.state = state;

            this.zip = zip;

            this.country = country;

        }

    }

 

Now what I’m going to do is:

 

·        Create a generic list of Person class.

·        Hard code some Person’s IDs, Names, phone numbers etc; and fill that list.

·        Store that list in a class level variable.

·        Set lstPerson.DataSource to list of persons.

·        Create a button in front of phone number text box and write code behind click event of that button.

·        Write code behind selected index changed event of the listbox.

 

Let’s start doing this step-by-step, that’s how our frmPersons.cs file starts:

 

namespace prjMakePhoneCall

{

    // Line numbers are given for understanding and are not part of the actual code

    public partial class frmPersons : Form

    {

01      private TapiManager tapiManager = new TapiManager(“prjMakePhoneCall”);

02      private List<Person> lstPerson = new List<Person>();

03      private string lineName, logEntry = string.Empty;

 

04      public frmPersons()

        {

            InitializeComponent();

        }

 

At line 01, TapiManager type variable is declared at class level. At line 02, I’m creating a class level variable which will contain all the persons information used for this application. Line 03 has two string variables lineName will keep the name of the telephone line tapi manager will use to make phone calls. logEntry will keep all the log of the phone calls made or attempted to make during an application session. Line 04 is standard form constructor. Now let’s see form load event:

 

// Line numbers are given for understanding and are not part of the actual code

private void frmPersons_Load(object sender, EventArgs e)

        {

01          tapiManager.Initialize();

02          this.GetPersonList();

03          this.ShowData();

04          this.lineName = (tapiManager != null && tapiManager.Lines.Length > 0 ? tapiManager.Lines[0].Name : string.Empty);

        }

 

Line 01 initializes form level tapiManager. In line 02 I’m calling GetPersonList() method which will create a list of persons. Person information is hard coded in this method and then saved in class level lstPersons variable. The same list of person will be displayed in our lstNames listbox in the method ShowData(), line 03. In real world application, GetPersonList() method will get list of persons from database instead of getting hard coded persons. Line 04 sets the name of the telephone line. When we call tapiManager’s initialize method it gets a list of all the lines attached to the computer, but we are interested in only the one connected with modem, which in most cases is present at 0^th index. Now let’s see our GetPersonList():

 

/// <summary>

/// Instead of hard coding Persons’ names you can get persons

/// from Database

/// </summary>

/// <returns></returns>

private List<Person> GetPersonList()

{

lstPerson.Add(new Person(1, “Roger”, “9,1-262-527-0200”, “New York”, “New York”, “24234”, “USA”));

      lstPerson.Add(new Person(2, “Kishor”, “6-692-1234”, “Banglore”, “Mahrashtra”, “4426”, “India”));

      lstPerson.Add(new Person(3, “Allmand”, “262-532-3415”, “Milwaukee”, “Wisconsin”, “52342”, “USA”));

      lstPerson.Add(new Person(4, “Chris”, “262-532-3416”, string.Empty, “California”, string.Empty, “USA”));

      lstPerson.Add(new Person(5, “Ahmed”, “051-2856021”, “Islamabad”, “Federal Capital”, “44000”, “Pakistan” ));

      return lstPerson;

}

 

Quite simple and straight forward, no explanation needed for this method. Let’s quickly jump to ShowData() method.

 

  private void ShowData()

        {

            this.lstNames.DisplayMember = “Name”;

            this.lstNames.ValueMember = “ID”;

            this.lstNames.DataSource = lstPerson;

        }

 

This method is even simpler than the previous one. Now let’s take a look at lstNames’s selected index change event:

 

private void lstNames_SelectedIndexChanged(object sender, EventArgs e)

        {           

            this.txtID.Text = this.lstPerson[this.lstNames.SelectedIndex].ID.ToString();

            this.txtName.Text = this.lstPerson[this.lstNames.SelectedIndex].Name;

            this.txtPhone.Text = this.lstPerson[this.lstNames.SelectedIndex].Phone;

            this.txtCity.Text = this.lstPerson[this.lstNames.SelectedIndex].City;

            this.txtState.Text = this.lstPerson[this.lstNames.SelectedIndex].State;

            this.txtZip.Text = this.lstPerson[this.lstNames.SelectedIndex].Zip;

            this.txtCountry.Text = this.lstPerson[this.lstNames.SelectedIndex].Country;

        }

 

For simplicity, I’ve used the selected index property of the listbox to refer the person in the generic list of persons, a class level variable. In real world application this logic won’t be that simple. Before I jump to the method which actually makes phone calls for us let me explain a few very important methods that are responsible for some functionality like log entry and closing the application and shutting down the tapiManager. So let’s take a look at them one by one.

 

private void frmPersons_FormClosed(object sender, FormClosedEventArgs e)

        {

            tapiManager.Shutdown();

            Application.ExitThread();

        }

 

When form is closed I want to shut down tapiManager and since this is the only form in my application, I want to exit the application thread as well.

 

        private void frmPersons_FormClosing(object sender, FormClosingEventArgs e)

        {

            StreamWriter logWriter = new StreamWriter(ConfigurationSettings.AppSettings[“LogFilePath”], true);

            try

            {

                string[] logEntries = this.logEntry.Split(‘|’);

                for (int i = 0; i < logEntries.Length; i++)

                    logWriter.WriteLine(logEntries[i]);

            }

            catch (Exception exc)

            { }

            finally

            {

                logWriter.Flush();

                logWriter.Close();

            }

        }

 

When form is closing I want all the activity done during the form was open to be saved in a log file. For this purpose I keep on saving user’s each and every activity in a class level string variable separated by “|” sign (explained below) and in this event I open a log file with stream writer, split the string on the basis of “|” and insert activities line by line.

 

After all these methods this is the time for showing and explaining what magic the phone button does which actually makes a phone call.

 

private void btnCall_Click(object sender, EventArgs e)

        {

            if(this.txtPhone.Text.Trim().Length > 0)

                this.MakePhoneCall(this.txtPhone.Text);

        }

 

When Call button is clicked, it simply checks the phone number text box’s text length. If it is more than 0 then it passes it to MakePhoneCall method.

 

private void MakePhoneCall(string phoneNumber)

{

01    TapiLine line = tapiManager.GetLineByName(this.lineName, true);

02    if (line != null)

      {

03          if (!line.IsOpen)

04                line.Open(MediaModes.DataModem);

 

05          line.NewCall += new EventHandler<NewCallEventArgs>(line_NewCall);

06          line.CallInfoChanged += new EventHandler<CallInfoChangeEventArgs>(line_CallInfoChanged);

07          line.CallStateChanged += new EventHandler<CallStateEventArgs>(line_CallStateChanged);

 

08          if (phoneNumber.Length > 0)

            {

09                MakeCallParams makeCallParams = new MakeCallParams();

10                makeCallParams.DialPause = 2000;

                  try

                  {

11                      TapiCall call = line.MakeCall(phoneNumber, null, makeCallParams);

12                      this.MakeLogEntry(“Created call “ + phoneNumber + ” -> “ + call, “Sending…”);

                  }

                  catch (Exception exc)

                  {

13                      if (exc.Message.IndexOf(“[0x80000005]”) > -1 && tapiManager != null)

                        {

14                          tapiManager.Shutdown();

15                          tapiManager = new TapiManager(“prjMakePhoneCall”);

16                          if (tapiManager.Initialize())

17                              this.MakePhoneCall(phoneNumber);

                        }

                  }

            }

      }

}

 

TapiLine is one of the classes given in Atapi.dll. This class is created by tapiManager’s method GetLineByName, line 01. After checking line object for not being null (line 02) we are ready to open the line for making a phone call. Lines 03, 04 check whether line is not open already, if not then open the line passing enum MediaModes’s DataModem. Lines 05, 06 and 07 are assigning event handler methods to different events line object generates while making a phone call. Line 08 double checks whether the phone number is not empty. Line 09 instantiates parameters object of Atapi library. This object can be used for different kind of settings in phone making process; e.g. I set dial pause to 2000 (2 second). Dial pause means when line opens and detects tone, after detecting the tone it will give a pause of 2 seconds. This is useful if you are sitting in your office and your desk phone is connected with a telephone exchange and you need to enter a number to get out of exchange and then you can enter outside number. You can do so by entering a number in textbox, prefixed by the number that takes you to out of telephone exchange, suffixed by a comma “,”. For example, I have to enter 9 to make outside phone calls in my office; I would enter a number 9,262-527-1234. 9 would take me out of the local phone exchange “,” will give a 2 second dial pause and then rest of the number will be dialed. After making ground, we are now ready to make phone call; line 11 is calling MakeCall method of line object. This will return a Call object which can be used in making log entry. Sometimes line’s MakeCall method throws an exception. I could not understand the reason and found the error is generated on random basis. The work around is given in the catch block; if exception has 0x80000005 number in its text then all we need to do is, shutdown tapiManager, re-initialize it and call the call MakePhoneCall method recursively. That’s exactly what I’m doing in lines 14, 15, 16 and 17.

 

 

 

 

 

 

 

 

After MakePhoneCall method there is nothing of vital importance in this code. So let’s just quickly see what event handlers of line object are doing.

 

  private void line_NewCall(object sender, NewCallEventArgs e)

        {

            this.MakeLogEntry(“New call: “ + e.Call, e.Privilege.ToString());

        }

 

        private void line_CallStateChanged(object sender, CallStateEventArgs e)

        {

            this.MakeLogEntry(“CallState: “ + e.Call.ToString(), e.CallState.ToString());

        }

 

        private void line_CallInfoChanged(object sender, CallInfoChangeEventArgs e)

        {

            this.MakeLogEntry(“CallInfo: “ + e.Call.ToString(), e.Change.ToString());

        }

 

All of these methods are just making log entries. Now let’s take a look at MakeLogEntry method which is even simpler than the above ones:

 

        private void MakeLogEntry(string callInfo, string status)

        {

            this.logEntry += DateTime.Now.ToShortDateString() + ” “ + DateTime.Now.ToLongTimeString() + ” : “ + callInfo + “, “ + status + “|”;

        }

 

This method prefixes date and time stamp with every log entry sent by any method. After running a couple of test calls, call log on my machine looks like this:

 

 

 

 

 

Before I end this article, for novice programmers, I want to show how you have to connect telephone chords with phone and computer. For this purpose you need 3 chords, one connected to landline port on the wall like this:

Secondly, this chord should be connected to a connector with two other wires as shown below:

One of these two chords would go into the computer’s modem like this:

And finally the last chord needs to go in the telephone set:

That’s it, simple and clean. After creating this demo application, you have become a savvy programmer who can develop .NET applications having ability to make phone calls. Don’t forget to give me your feedback on this article and also feel free to contact me if you have any questions.

 

 

Hasta La Vista folks…