Correct variable names in Echo activity (dotnet#3247)

docs/framework/wcf/feature-details/how-to-access-a-service-from-a-workflow-application.md

@@ -54,7 +54,7 @@ This topic describes how to call a workflow service from a workflow console appl
 
      ![Adding a variable](../../../../docs/framework/wcf/feature-details/media/instringvar.JPG "inStringVar")  
 
-9. Drag and drop an **Echo** activity into the <!--zz <xref:System.ServiceModel.Activities.Sequence>--> `System.ServiceModel.Activities.Sequence`. In the properties window bind the _string argument to the `inString` variable and the `out_string` argument to the outString variable as shown in the following illustration. This passes in the value of the `inString` variable to the operation and then takes the return value and places it in the `outString` variable.  
+9. Drag and drop an **Echo** activity into the <!--zz <xref:System.ServiceModel.Activities.Sequence>--> `System.ServiceModel.Activities.Sequence`. In the properties window bind the `inMsg` argument to the `inString` variable and the `outMsg` argument to the `outString` variable as shown in the following illustration. This passes in the value of the `inString` variable to the operation and then takes the return value and places it in the `outString` variable.  
 
      ![Binding the arguments to variables](../../../../docs/framework/wcf/feature-details/media/argumentbind.JPG "ArgumentBind")