AWS SDK Version 3 for .NET
API Reference

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Sends user input (text-only) to Amazon Lex. Client applications can use this API to send requests to Amazon Lex at runtime. Amazon Lex then interprets the user input using the machine learning model it built for the bot.

In response, Amazon Lex returns the next message to convey to the user an optional responseCard to display. Consider the following example messages:

Not all Amazon Lex messages require a user response. For example, a conclusion statement does not require a response. Some messages require only a "yes" or "no" user response. In addition to the message, Amazon Lex provides additional context about the message in the response that you might use to enhance client behavior, for example, to display the appropriate client user interface. These are the slotToElicit, dialogState, intentName, and slots fields in the response. Consider the following examples:

In addition, Amazon Lex also returns your application-specific sessionAttributes. For more information, see Managing Conversation Context.


For .NET Core and PCL this operation is only available in asynchronous form. Please refer to PostTextAsync.

Namespace: Amazon.Lex
Assembly: AWSSDK.Lex.dll
Version: 3.x.y.z


public abstract PostTextResponse PostText(
         PostTextRequest request
Type: Amazon.Lex.Model.PostTextRequest

Container for the necessary parameters to execute the PostText service method.

Return Value
The response from the PostText service method, as returned by Lex.


BadGatewayException Either the Amazon Lex bot is still building, or one of the dependent services (Amazon Polly, AWS Lambda) failed with an internal service error.
BadRequestException Request validation failed, there is no usable message in the context, or the bot build failed, is still in progress, or contains unbuilt changes.
ConflictException Two clients are using the same AWS account, Amazon Lex bot, and user ID.
DependencyFailedException One of the dependencies, such as AWS Lambda or Amazon Polly, threw an exception. For example, If Amazon Lex does not have sufficient permissions to call a Lambda function. If a Lambda function takes longer than 30 seconds to execute. If a fulfillment Lambda function returns a Delegate dialog action without removing any slot values.
InternalFailureException Internal service error. Retry the call.
LimitExceededException Exceeded a limit.
LoopDetectedException This exception is not used.
NotFoundException The resource (such as the Amazon Lex bot or an alias) that is referred to is not found.

Version Information

.NET Framework:
Supported in: 4.5, 4.0, 3.5

Portable Class Library:
Supported in: Windows Store Apps
Supported in: Windows Phone 8.1
Supported in: Xamarin Android
Supported in: Xamarin iOS (Unified)
Supported in: Xamarin.Forms

See Also