If you want to apply conditional validation on 'City Code' or 'Country Code' then you need to add this input as 'Delhi'.
{{locationFormGroup.controls.areaName.errors.alphaNumeric.message}}
This allowed whitespace in alpha Numeric validation
{{locationFormGroup.controls.flatAddress.errors.alphaNumeric.message}}
Shows custom message
{{locationFormGroup.controls.postalAddress.errors.alphaNumeric.message}}
If you want to apply conditional validation on this field then you need to add 'areaName' input as 'Delhi'.
Conditional Expression with type 'string'
{{locationFormGroup.controls.cityCode.errors.alphaNumeric.message}}