How to identify Required fields via the API
107530
How to tell whether a field is required or not in Apex by describe fields
155969
Required Attribute on Generic List Property
33900
Verifying a signature in Apex
108587
How can I get a complete list of fields for a standard object?
33881
How to get image name, mime type, width, height, file size from post custom field?
24613
Get name of a field
145489
How to perform entity validation on code level?
48944
removing field name from validation error message
39397
How do I programmatically update the allowed values of a list field?
108444
Correct way to validate config entities?
914
How to set MINIMUM number of required fields?
938
How can I get the list of all fields(API name,Label,type) of any sObject?
134097
Accessing an object's fields without an active session
36811
How do I access a field value for an entity (e.g. node) object?
48472
What's the best way to highlight a Required field on a web form before submission?
96559
Account Required Field Missing on Lead Conversion
36779
How to make a field required to enter a specific number?