Modify Calls In Progress With C#

In this guide we’ll show you how to manipulate live phone calls using C#. We’ll also cover how to retrieve information about in progress and completed calls from your Twilio account.

The code snippets in this guide are written using modern C# language features and require the .NET Framework version 4.5 or higher. They also make use of the Twilio C# SDK.

Modifying Twilio phone calls in progress with C#

The simplest way to control the flow of a Twilio phone call is with TwiML itself.

You can use the "action" parameters of verbs like <Gather> and <Record> to tell Twilio to get new instructions from your applications during a call. You can also use the <Redirect> verb to explicitly tell Twilio to fetch new TwiML.

But sometimes you need to change a live phone call outside of Twilio’s normal request-response cycle. For those cases you can use "RedirectCall()" to tell Twilio to immediately change the TwiML it’s using in a phone call.

Loading Code Samples...
Language
SDK Version:
  • 4.x
  • 5.x
Format:
  • JSON
  • XML
// Download the twilio-csharp library from twilio.com/docs/csharp/install
using System;
using Twilio;
class Example 
{
  static void Main(string[] args) 
  {
    // Find your Account Sid and Auth Token at twilio.com/user/account
    string AccountSid = "ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
    string AuthToken = "your_auth_token";
    var twilio = new TwilioRestClient(AccountSid, AuthToken);

    twilio.RedirectCall("CAe1644a7eed5088b159577c5802d8be38", 
        "http://demo.twilio.com/docs/voice.xml", "POST");
  }
}
// Download the twilio-csharp library from twilio.com/docs/libraries/csharp
using System;
using Twilio;
using Twilio.Http;
using Twilio.Rest.Api.V2010.Account;

class Example
{
    static void Main(string[] args)
    {
        // Find your Account Sid and Auth Token at twilio.com/console
        const string accountSid = "ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
        const string authToken = "your_auth_token";
        TwilioClient.Init(accountSid, authToken);

        CallResource.Update(
            "CAe1644a7eed5088b159577c5802d8be38",
            url: new Uri("http://demo.twilio.com/docs/voice.xml"),
            method: HttpMethod.Post);
    }
}
{
	"sid": "CAe1644a7eed5088b159577c5802d8be38",
	"date_created": "Tue, 10 Aug 2010 08:02:17 +0000",
	"date_updated": "Tue, 10 Aug 2010 08:02:47 +0000",
	"parent_call_sid": null,
	"account_sid": "ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX",
	"to": "+14153855708",
	"from": "+14158141819",
	"phone_number_sid": null,
	"status": "in-progress",
	"start_time": "Tue, 10 Aug 2010 08:02:31 +0000",
	"end_time": "Tue, 10 Aug 2010 08:02:47 +0000",
	"duration": "16",
	"price": "-0.03000",
	"direction": "outbound-api",
	"answered_by": null,
	"api_version": "2010-04-01",
	"annotation": null,
	"forwarded_from": null,
	"caller_name": null,
	"uri": "\/2010-04-01\/Accounts\/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX\/Calls\/CAe1644a7eed5088b159577c5802d8be38.json",
	"subresource_uris":{
		"notifications": "\/2010-04-01\/Accounts\/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX\/Calls\/CAe1644a7eed5088b159577c5802d8be38\/Notifications.json",
		"recordings": "\/2010-04-01\/Accounts\/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX\/Calls\/CAe1644a7eed5088b159577c5802d8be38\/Recordings.json"
	}
}
<TwilioResponse>
	<Call>
		<Sid>CAe1644a7eed5088b159577c5802d8be38</Sid>
		<DateCreated>Tue, 10 Aug 2010 08:02:17 +0000</DateCreated>
		<DateUpdated>Tue, 10 Aug 2010 08:02:47 +0000</DateUpdated>
		<ParentCallSid/>
		<AccountSid>ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX</AccountSid>
		<To>+14153855708</To>
		<From>+14158141819</From>
		<PhoneNumberSid></PhoneNumberSid>
		<Status>in-progress</Status>
		<StartTime>Tue, 10 Aug 2010 08:02:31 +0000</StartTime>
		<EndTime>Tue, 10 Aug 2010 08:02:47 +0000</EndTime>
		<Duration>16</Duration>
		<Price>-0.03000</Price>
		<Direction>outbound-api</Direction>
		<AnsweredBy/>
		<ApiVersion>2010-04-01</ApiVersion>
		<ForwardedFrom/>
		<CallerName/>
		<Uri>/2010-04-01/Accounts/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/Calls/CAe1644a7eed5088b159577c5802d8be38</Uri>
		<SubresourceUris>
			<Notifications>/2010-04-01/Accounts/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/Calls/CAe1644a7eed5088b159577c5802d8be38/Notifications</Notifications>
			<Recordings>/2010-04-01/Accounts/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/Calls/CAe1644a7eed5088b159577c5802d8be38/Recordings</Recordings>
		</SubresourceUris>
	</Call>
</TwilioResponse>
Redirect a Running Call to a New URL

To update a call in progress you must provide:

  • CallSid - Twilio returns a CallSid when you initiate an outgoing call. Twilio also includes the CallSid in its request to your application for an incoming call’s initial TwiML.
  • Url - The URL Twilio should use to request new TwiML from your application.

Hanging up a call in progress

Twilio will end phone calls for you when it encounters a <Hangup> verb or when it runs out of TwiML to process. But you can also end phone calls whenever you like by passing a "completed" status to a CallSid in progress.

Loading Code Samples...
Language
SDK Version:
  • 4.x
  • 5.x
Format:
  • JSON
  • XML
// Download the twilio-csharp library from twilio.com/docs/csharp/install
using System;
using Twilio;
class Example 
{
  static void Main(string[] args) 
  {
    // Find your Account Sid and Auth Token at twilio.com/user/account
    string AccountSid = "ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
    string AuthToken = "your_auth_token";
    var twilio = new TwilioRestClient(AccountSid, AuthToken);

    twilio.HangupCall("CAe1644a7eed5088b159577c5802d8be38", HangupStyle.Completed);
  }
}
// Download the twilio-csharp library from twilio.com/docs/libraries/csharp
using System;
using Twilio;
using Twilio.Rest.Api.V2010.Account;

class Example
{
    static void Main(string[] args)
    {
        // Find your Account Sid and Auth Token at twilio.com/console
        const string accountSid = "ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
        const string authToken = "your_auth_token";
        TwilioClient.Init(accountSid, authToken);

        CallResource.Update("CAe1644a7eed5088b159577c5802d8be38",
                            status: CallResource.UpdateStatusEnum.Completed);
    }
}
{
	"sid": "CAe1644a7eed5088b159577c5802d8be38",
	"date_created": "Tue, 10 Aug 2010 08:02:17 +0000",
	"date_updated": "Tue, 10 Aug 2010 08:02:47 +0000",
	"parent_call_sid": null,
	"account_sid": "ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX",
	"to": "+14153855708",
	"from": "+14158141819",
	"phone_number_sid": null,
	"status": "completed",
	"start_time": "Tue, 10 Aug 2010 08:02:31 +0000",
	"end_time": "Tue, 10 Aug 2010 08:02:47 +0000",
	"duration": "16",
	"price": "-0.03000",
	"direction": "outbound-api",
	"answered_by": null,
	"api_version": "2010-04-01",
	"annotation": null,
	"forwarded_from": null,
	"caller_name": null,
	"uri": "\/2010-04-01\/Accounts\/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX\/Calls\/CAe1644a7eed5088b159577c5802d8be38.json",
	"subresource_uris":{
		"notifications": "\/2010-04-01\/Accounts\/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX\/Calls\/CAe1644a7eed5088b159577c5802d8be38\/Notifications.json",
		"recordings": "\/2010-04-01\/Accounts\/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX\/Calls\/CAe1644a7eed5088b159577c5802d8be38\/Recordings.json"
	}
}
<TwilioResponse>
	<Call>
		<Sid>CAe1644a7eed5088b159577c5802d8be38</Sid>
		<DateCreated>Tue, 10 Aug 2010 08:02:17 +0000</DateCreated>
		<DateUpdated>Tue, 10 Aug 2010 08:02:47 +0000</DateUpdated>
		<ParentCallSid/>
		<AccountSid>ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX</AccountSid>
		<To>+14153855708</To>
		<From>+14158141819</From>
		<PhoneNumberSid></PhoneNumberSid>
		<Status>completed</Status>
		<StartTime>Tue, 10 Aug 2010 08:02:31 +0000</StartTime>
		<EndTime>Tue, 10 Aug 2010 08:02:47 +0000</EndTime>
		<Duration>16</Duration>
		<Price>-0.03000</Price>
		<Direction>outbound-api</Direction>
		<AnsweredBy/>
		<ApiVersion>2010-04-01</ApiVersion>
		<ForwardedFrom/>
		<CallerName/>
		<Uri>/2010-04-01/Accounts/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/Calls/CAe1644a7eed5088b159577c5802d8be38</Uri>
		<SubresourceUris>
			<Notifications>/2010-04-01/Accounts/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/Calls/CAe1644a7eed5088b159577c5802d8be38/Notifications</Notifications>
			<Recordings>/2010-04-01/Accounts/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/Calls/CAe1644a7eed5088b159577c5802d8be38/Recordings</Recordings>
		</SubresourceUris>
	</Call>
</TwilioResponse>
Terminate a Running Call

Check out Modifying Live Calls in the reference docs for more details.

Where to next?

Check out our tutorials to see full implementations of Twilio Voice in C# with ASP.NET.

David Prothero
Agustin Camino
Rob Spectre
Ricky Robinett
Kat King
Andrew Baker
Kevin Whinnery

Need some help?

We all do sometimes; code is hard. Get help now from our support team, or lean on the wisdom of the crowd browsing the Twilio tag on Stack Overflow.

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Loading Code Samples...
SDK Version:
  • 4.x
  • 5.x
Format:
  • JSON
  • XML
// Download the twilio-csharp library from twilio.com/docs/csharp/install
using System;
using Twilio;
class Example 
{
  static void Main(string[] args) 
  {
    // Find your Account Sid and Auth Token at twilio.com/user/account
    string AccountSid = "ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
    string AuthToken = "your_auth_token";
    var twilio = new TwilioRestClient(AccountSid, AuthToken);

    twilio.RedirectCall("CAe1644a7eed5088b159577c5802d8be38", 
        "http://demo.twilio.com/docs/voice.xml", "POST");
  }
}
// Download the twilio-csharp library from twilio.com/docs/libraries/csharp
using System;
using Twilio;
using Twilio.Http;
using Twilio.Rest.Api.V2010.Account;

class Example
{
    static void Main(string[] args)
    {
        // Find your Account Sid and Auth Token at twilio.com/console
        const string accountSid = "ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
        const string authToken = "your_auth_token";
        TwilioClient.Init(accountSid, authToken);

        CallResource.Update(
            "CAe1644a7eed5088b159577c5802d8be38",
            url: new Uri("http://demo.twilio.com/docs/voice.xml"),
            method: HttpMethod.Post);
    }
}
{
	"sid": "CAe1644a7eed5088b159577c5802d8be38",
	"date_created": "Tue, 10 Aug 2010 08:02:17 +0000",
	"date_updated": "Tue, 10 Aug 2010 08:02:47 +0000",
	"parent_call_sid": null,
	"account_sid": "ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX",
	"to": "+14153855708",
	"from": "+14158141819",
	"phone_number_sid": null,
	"status": "in-progress",
	"start_time": "Tue, 10 Aug 2010 08:02:31 +0000",
	"end_time": "Tue, 10 Aug 2010 08:02:47 +0000",
	"duration": "16",
	"price": "-0.03000",
	"direction": "outbound-api",
	"answered_by": null,
	"api_version": "2010-04-01",
	"annotation": null,
	"forwarded_from": null,
	"caller_name": null,
	"uri": "\/2010-04-01\/Accounts\/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX\/Calls\/CAe1644a7eed5088b159577c5802d8be38.json",
	"subresource_uris":{
		"notifications": "\/2010-04-01\/Accounts\/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX\/Calls\/CAe1644a7eed5088b159577c5802d8be38\/Notifications.json",
		"recordings": "\/2010-04-01\/Accounts\/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX\/Calls\/CAe1644a7eed5088b159577c5802d8be38\/Recordings.json"
	}
}
<TwilioResponse>
	<Call>
		<Sid>CAe1644a7eed5088b159577c5802d8be38</Sid>
		<DateCreated>Tue, 10 Aug 2010 08:02:17 +0000</DateCreated>
		<DateUpdated>Tue, 10 Aug 2010 08:02:47 +0000</DateUpdated>
		<ParentCallSid/>
		<AccountSid>ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX</AccountSid>
		<To>+14153855708</To>
		<From>+14158141819</From>
		<PhoneNumberSid></PhoneNumberSid>
		<Status>in-progress</Status>
		<StartTime>Tue, 10 Aug 2010 08:02:31 +0000</StartTime>
		<EndTime>Tue, 10 Aug 2010 08:02:47 +0000</EndTime>
		<Duration>16</Duration>
		<Price>-0.03000</Price>
		<Direction>outbound-api</Direction>
		<AnsweredBy/>
		<ApiVersion>2010-04-01</ApiVersion>
		<ForwardedFrom/>
		<CallerName/>
		<Uri>/2010-04-01/Accounts/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/Calls/CAe1644a7eed5088b159577c5802d8be38</Uri>
		<SubresourceUris>
			<Notifications>/2010-04-01/Accounts/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/Calls/CAe1644a7eed5088b159577c5802d8be38/Notifications</Notifications>
			<Recordings>/2010-04-01/Accounts/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/Calls/CAe1644a7eed5088b159577c5802d8be38/Recordings</Recordings>
		</SubresourceUris>
	</Call>
</TwilioResponse>
SDK Version:
  • 4.x
  • 5.x
Format:
  • JSON
  • XML
// Download the twilio-csharp library from twilio.com/docs/csharp/install
using System;
using Twilio;
class Example 
{
  static void Main(string[] args) 
  {
    // Find your Account Sid and Auth Token at twilio.com/user/account
    string AccountSid = "ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
    string AuthToken = "your_auth_token";
    var twilio = new TwilioRestClient(AccountSid, AuthToken);

    twilio.HangupCall("CAe1644a7eed5088b159577c5802d8be38", HangupStyle.Completed);
  }
}
// Download the twilio-csharp library from twilio.com/docs/libraries/csharp
using System;
using Twilio;
using Twilio.Rest.Api.V2010.Account;

class Example
{
    static void Main(string[] args)
    {
        // Find your Account Sid and Auth Token at twilio.com/console
        const string accountSid = "ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
        const string authToken = "your_auth_token";
        TwilioClient.Init(accountSid, authToken);

        CallResource.Update("CAe1644a7eed5088b159577c5802d8be38",
                            status: CallResource.UpdateStatusEnum.Completed);
    }
}
{
	"sid": "CAe1644a7eed5088b159577c5802d8be38",
	"date_created": "Tue, 10 Aug 2010 08:02:17 +0000",
	"date_updated": "Tue, 10 Aug 2010 08:02:47 +0000",
	"parent_call_sid": null,
	"account_sid": "ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX",
	"to": "+14153855708",
	"from": "+14158141819",
	"phone_number_sid": null,
	"status": "completed",
	"start_time": "Tue, 10 Aug 2010 08:02:31 +0000",
	"end_time": "Tue, 10 Aug 2010 08:02:47 +0000",
	"duration": "16",
	"price": "-0.03000",
	"direction": "outbound-api",
	"answered_by": null,
	"api_version": "2010-04-01",
	"annotation": null,
	"forwarded_from": null,
	"caller_name": null,
	"uri": "\/2010-04-01\/Accounts\/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX\/Calls\/CAe1644a7eed5088b159577c5802d8be38.json",
	"subresource_uris":{
		"notifications": "\/2010-04-01\/Accounts\/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX\/Calls\/CAe1644a7eed5088b159577c5802d8be38\/Notifications.json",
		"recordings": "\/2010-04-01\/Accounts\/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX\/Calls\/CAe1644a7eed5088b159577c5802d8be38\/Recordings.json"
	}
}
<TwilioResponse>
	<Call>
		<Sid>CAe1644a7eed5088b159577c5802d8be38</Sid>
		<DateCreated>Tue, 10 Aug 2010 08:02:17 +0000</DateCreated>
		<DateUpdated>Tue, 10 Aug 2010 08:02:47 +0000</DateUpdated>
		<ParentCallSid/>
		<AccountSid>ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX</AccountSid>
		<To>+14153855708</To>
		<From>+14158141819</From>
		<PhoneNumberSid></PhoneNumberSid>
		<Status>completed</Status>
		<StartTime>Tue, 10 Aug 2010 08:02:31 +0000</StartTime>
		<EndTime>Tue, 10 Aug 2010 08:02:47 +0000</EndTime>
		<Duration>16</Duration>
		<Price>-0.03000</Price>
		<Direction>outbound-api</Direction>
		<AnsweredBy/>
		<ApiVersion>2010-04-01</ApiVersion>
		<ForwardedFrom/>
		<CallerName/>
		<Uri>/2010-04-01/Accounts/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/Calls/CAe1644a7eed5088b159577c5802d8be38</Uri>
		<SubresourceUris>
			<Notifications>/2010-04-01/Accounts/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/Calls/CAe1644a7eed5088b159577c5802d8be38/Notifications</Notifications>
			<Recordings>/2010-04-01/Accounts/ACXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/Calls/CAe1644a7eed5088b159577c5802d8be38/Recordings</Recordings>
		</SubresourceUris>
	</Call>
</TwilioResponse>