Hello Deepak ,
You can read some Reference Guide through this link below ---
https://world.mendix.com/display/refguide5/Reference+Selector .
I hope this link is some usefull for you.
The widget 'Input Reference Selector' currently doesn't work well with Validation Feedback messages.
I'd suggest filing a ticket.
I created a custom validation message by creating a SASS class for the reference selector .
.field-invalid .form-control, .field-invalid .form-disabled p, .form-disabled .field-valid p {
border-color: #A94442;
border-width: 2px;
color: #A94442;
}
Then I set this new reference selector and validation message to appear based on a boolean.
Create a container and input validation message and set the styling to
color: #F7DCDB;
background-color: #F7DCDB;
margin-top: 0.5em;
padding: 1em;
border-radius: 4px;