C#•10mo ago

Some help with foreign key in .net

When im trying to add a foreign key to a table it shows an error "ALTER table "

14 Replies

canton7•10mo ago

I'm afraid we need significantly more information to help you. * What is the structure of the table you're trying to add a foreign key to? * What is the foreign key pointing to? * What is the exact, full error message you've got?

ShuajbM•10mo ago

i have 2 tables : Puna(it means Jobs) and Categories . In Category i have attributes like :

c#
public class Category
{
    [Key]
    public int Id { get; set; }
    [Required]
    [DisplayName("Emri i kategorise")]
    [MaxLength(30)]
    public string Name { get; set; }

    [DisplayName("Display Order")]
    [Range(1, 100)]
    public int DisplayOrder { get; set; }

c#
public class Category
{
    [Key]
    public int Id { get; set; }
    [Required]
    [DisplayName("Emri i kategorise")]
    [MaxLength(30)]
    public string Name { get; set; }

    [DisplayName("Display Order")]
    [Range(1, 100)]
    public int DisplayOrder { get; set; }

i added this table to mssql correctly so i did this migration through console and it was added successfully then i have other class Puna(Jobs) with those attributes:

c#
public class Puna
{
    [Key]
    public int Id { get; set; }

    [Required]
    [MaxLength(100)]
    [DisplayName("Pozita e Punes")]
    public string Emri_Pozites {  get; set; }

    [Required]
    [MaxLength(100)]
    public string Pershkrimi { get; set; }
    [Required]
    public string Kerkesat { get; set; }
    [Required]
    public string Lokacioni { get; set; }

    public string ImageUrl { get; set; }

    public int CategoryId { get; set; }
    [ForeignKey("CategoryId")]
    public Category Category { get; set; }

    

}

c#
public class Puna
{
    [Key]
    public int Id { get; set; }

    [Required]
    [MaxLength(100)]
    [DisplayName("Pozita e Punes")]
    public string Emri_Pozites {  get; set; }

    [Required]
    [MaxLength(100)]
    public string Pershkrimi { get; set; }
    [Required]
    public string Kerkesat { get; set; }
    [Required]
    public string Lokacioni { get; set; }

    public string ImageUrl { get; set; }

    public int CategoryId { get; set; }
    [ForeignKey("CategoryId")]
    public Category Category { get; set; }

    

}

Jimmacle•10mo ago

why aren't you using migrations? oh, you did

ShuajbM•10mo ago

im using them

Jimmacle•10mo ago

i misread i added this table to mssql correctly to mean you weren't

ShuajbM•10mo ago

then when i try to add these foreign key when i add migration then update-database it shows this : "The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_Punet_Categories_CategoryId". The conflict occurred in database "Jobify", table "dbo.Categories", column 'Id'." i dont have this attribute still in my database

Jimmacle•10mo ago

isn't the ForeignKey attribute supposed to go on the key property, not the navigation property? technically you don't need it at all as it should be figured out by convention

ShuajbM•10mo ago

idk im facing this error about 2 days watched some videos still didnt get the result i want

Jimmacle•10mo ago

the official documentation is the best place to look

Jimmacle•10mo ago

https://learn.microsoft.com/en-us/ef/core/modeling/relationships/mapping-attributes#foreignkeyattribute

Mapping attributes (aka Data Annotations) for relationships - EF Core

Using mapping attributes (also know as Data Annotations) to configure Entity Framework Core relationships

Jimmacle•10mo ago

i guess that attribute works both ways

ShuajbM•10mo ago

so instead using ForeignKey annotation maybe use this [ForeignKey(nameof(Blog))] still it doesnt work how can i alter the table in console

Jimmacle•10mo ago

if you're using migrations, you don't altering the database schema outside of migrations is how you end up with problems like this

ShuajbM•10mo ago

so i should store them in another database ? i started in a new database and occured the same problem <<<<The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_Punet_Categories_CategoryId". The conflict occurred in database "Jobify", table "dbo.Categories", column 'Id'>>>>

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Some help with foreign key in .net