Lookup fields processing in custom activity

If you are using SharepointWorkflows with some custom activities you might face this problem.

In your custom activities, you might need dynamic content input from user while creating workflows.

Mail text would be the best example for the same.

In custom activity such as mail send with attachments, needs dynamic content.

For example,

Hi [%List:Username%]

.....

......

Thanks,

[%List:Sender%]

This kind of dynamic content will not be parse if you directly use the input parameter without Helper.ProcessStringField.

Without this processing custom activity will treat it as a string. and and in mail you will get Hi [%List:Username%] text. (instead of Hi Indrajeet..)

So to fix of the problem, 

before using the input in mailsend function you should procees it by using Helper.ProcessStringField(stringFromUserInput, objActivity, this.__Context))

Ex. String retValue = Helper.ProcessStringField(stringFromUserInput, objActivity, this.__Context))