Data Annotation

📌 Entity-Level (Class)

• [Table] → Maps an entity to a specific table (optionally with schema).

• [Index] (EF Core 5+) → Defines database indexes on properties.

• [Owned] → Marks a type as an owned entity.

• [Keyless] → Marks an entity as having no primary key (useful for views).

📌 Property-Level

• [Key] → Marks property as primary key.

• [Required] → Makes property non-nullable.

• [MaxLength] / [MinLength] / [StringLength] → Controls string/array length.

• [Column] → Configures column name, type, and order.

• [DatabaseGenerated] → Specifies value generation strategy (Identity, Computed, None).

• [ConcurrencyCheck] → Marks property for optimistic concurrency.

• [Timestamp] → Special concurrency token (rowversion).

• [NotMapped] → Excludes property from database mapping.

• [Precision] (EF Core 6+) → Sets precision and scale for decimals.

📌 Relationship-Level

• [ForeignKey] → Marks property as foreign key.

• [InverseProperty] → Specifies the inverse navigation property.

• [Required] (on navigation) → Ensures relationship is not optional.

📌 Validation-Oriented (from DataAnnotations)

• [Range] → Numeric/date range validation.

• [RegularExpression] → Regex validation.

• [EmailAddress], [Phone], [Url], [CreditCard] → Specialized format validation.

• [Compare] → Compare two properties (e.g., password confirmation).

• [Display], [DisplayFormat], [DataType] → UI metadata and formatting.

• [Editable], [ScaffoldColumn] → UI scaffolding hints.

https://learn.microsoft.com/en-us/dotnet/api/system.componentmodel.dataannotations?view=net-8.0 

https://learn.microsoft.com/en-us/dotnet/api/system.componentmodel.dataannotations?view=net-7.0

https://www.c-sharpcorner.com/article/data-annotations-in-net/ 

https://blazor.syncfusion.com/documentation/data-form/data-annotation-attributes 

0. [ValidateNever]

When you have a property that should be bound but not validated.

Example: A navigation property in EF Core that you don’t want MVC to validate.

1. `[Required]`

The [Required] annotation ensures that a property cannot be null.

public class Person

{

           [Required]

           public string FirstName { get; set; }

}

2. `[StringLength]`

Defines the maximum and minimum length of a string property.

public class Product

{

           [StringLength(50, MinimumLength = 3)]

           public string Name { get; set; }

}

3. `[Range]`

Restricts a property to a specified numeric range.

public class Temperature

{

           [Range(-40, 100)]

           public int Celsius { get; set; }

}

4. `[RegularExpression]`

Validates a property against a regular expression pattern.

public class Email

{

           [RegularExpression(@"^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}$")]

           public string Address { get; set; }

}

5. `[Compare]`

Compares the values of two properties for equality.

public class User

{

           public string Password { get; set; }

           [Compare("Password")]

           public string ConfirmPassword { get; set; }

}

6. `[EmailAddress]`

Ensures that a string property contains a valid email address.

public class Contact

{

           [EmailAddress]

           public string Email { get; set; }

}

7. `[Phone]`

Validates a string property as a phone number.

public class Contact

{

           [Phone]

           public string PhoneNumber { get; set; }

}

8. `[Url]`

Check if a string property contains a valid URL.

public class Website

{

           [Url]

           public string URL { get; set; }

}

9. `[CreditCard]`

Ensures a string property contains a valid credit card number.

public class Payment

{

           [CreditCard]

           public string CardNumber { get; set; }

}

10. `[MaxLength]`

Specifies the maximum length of a string property.

public class Tweet

{

           [MaxLength(280)]

           public string Text { get; set; }

}

11. `[MinLength]`

Sets the minimum length for a string property.

public class Password

{

           [MinLength(8)]

           public string Value { get; set; }

}

12. `[DataType]`

Specifies the data type of a property.

public class Person

{

           [DataType(DataType.Date)]

           public DateTime BirthDate { get; set; }

}

13. `[Display]`

Customizes the display name for a property.

public class Product

{

           [Display(Name = "Product Name")]

           public string Name { get; set; }

}

14. `[ScaffoldColumn]`

Hides a property from a scaffolding in ASP.NET MVC.

public class Employee

{

           [ScaffoldColumn(false)]

           public int EmployeeID { get; set; }

}

15. `[ScaffoldTable]`

Specifies the table name for an Entity Framework Entity.

[ScaffoldTable("tbl_Product")]

public class Product

{

           public string Name { get; set; }

}

16. `[Editable]`

Determines whether a property is editable in MVC.

[Editable(false)]

public class UserProfile

{

           public string FirstName { get; set; }

}

17. `[Key]`

Marks a property as the primary key for an Entity Framework Entity.

public class Customer

{

           [Key]

[DatabaseGenerated(DatabaseGeneratedOption.Identity)]   //optional

           public int CustomerID { get; set; }

}

18. `[ForeignKey]`

Defines a foreign key relationship in Entity Framework.

public class Order

{

           public int CustomerID { get; set; }

           [ForeignKey("CustomerID")]

           public Customer Customer { get; set; }

}

19. `[Table]`

Specifies the table name for an Entity Framework entity.

[Table("Orders")]

public class Order

{

           public string OrderName { get; set; }

}

20. `[Column]`

Defines the column name for a property in Entity Framework.

public class User

{

           [Column("Full_Name")]

           public string FullName { get; set; }

}

21. `[ConcurrencyCheck]`

Indicates that a property should be included in optimistic concurrency checks.

public class Product

{

           [ConcurrencyCheck]

           public int UnitsInStock { get; set; }

}

22. `[Timestamp]`

Specifies that a property represents a database-generated timestamp.

public class Product

{

           [Timestamp]

           public byte[] RowVersion { get; set; }

}

23. `[DatabaseGenerated]`

Marks a property as database-generated.

public class Order

{

           [DatabaseGenerated(DatabaseGeneratedOption.Identity)]

           public int OrderID { get; set; }

}

24. `[NotMapped]`

Excludes a property from being mapped to the database.

public class User

{

           [NotMapped]

           public string FullName => $"{FirstName} {LastName}";

}

25. `[Bind]`

Specifies which properties should be included when binding data in an MVC action.

[Bind(Include = "FirstName, LastName, Email")]

public class UserProfile

{

           public string FirstName { get; set; }

           public string LastName { get; set; }

           public string Email { get; set; }

}