CODEWITHSUNDEEP
c#asp.netentity-frameworkasp.net-core.net-core
trevoirwilliams
trevoirwilliams

Reputation: 478

Entity Framework Core 2 - Foreign Key Constraint

I am trying to have a model with two references to another model.

I have researched this error, but have seen suggestions relating to previous .Net Core versions.

Below is the model

public class Match
{
    public int ID { get; set; }
    public DateTime MatchDateTime
    { get; set; }
    public int LocationID { get; set; }
    public int GroupID { get; set; }
    public int HomeTeamScore { get; set; }
    public int AwayTeamScore { get; set; }
    [Required]
    public int HomeTeamID { get; set; }
    public int AwayTeamID { get; set; }
    public Location Location { get; set; }
    public Group Group { get; set; }

    [Required]
    [ForeignKey("HomeTeamID")]
    public Team HomeTeam { get; set; }
    [ForeignKey("AwayTeamID")]
    public Team AwayTeam { get; set; }
}

Upon running the migration, i get this error:

Introducing FOREIGN KEY constraint 'FK_Matches_Teams_AwayTeamID' on table 'Matches' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.

Upvotes: 1

Views: 4098

Answers (2)

trevoirwilliams
trevoirwilliams

Reputation: 478

So..The solution was simple really.

I made the Foreign Key IDs nullable. I am not sure if making both nullable was 'required'

See the code below:

public class Match
{
public int ID { get; set; }
public DateTime MatchDateTime
{ get; set; }
public int LocationID { get; set; }
public int GroupID { get; set; }
public int HomeTeamScore { get; set; }
public int AwayTeamScore { get; set; }
public int? HomeTeamID { get; set; }
public int? AwayTeamID { get; set; }
public Location Location { get; set; }
public Group Group { get; set; }

[Required]
[ForeignKey("HomeTeamID")]
public Team HomeTeam { get; set; }
[ForeignKey("AwayTeamID")]
public Team AwayTeam { get; set; }

}

Upvotes: 1

Vivek Nuna
Vivek Nuna

Reputation: 1

When you run Add-Migration, it will generate migration file similar to the below code.

migrationBuilder.CreateTable(
name: "Match",
columns: table => new
{
    ID = table.Column<int>(nullable: false)
        .Annotation("SqlServer:ValueGenerationStrategy", SqlServerValueGenerationStrategy.IdentityColumn),
    AwayTeamID = table.Column<int>(nullable: false),
    AwayTeamScore = table.Column<int>(nullable: false),
    GroupID = table.Column<int>(nullable: false),
    HomeTeamID = table.Column<int>(nullable: false),
    HomeTeamScore = table.Column<int>(nullable: false),
    LocationID = table.Column<int>(nullable: false),
    MatchDateTime = table.Column<DateTime>(nullable: false)
},
constraints: table =>
{
    table.PrimaryKey("PK_Match", x => x.ID);
    table.ForeignKey(
        name: "FK_Match_Team_AwayTeamID",
        column: x => x.AwayTeamID,
        principalTable: "Team",
        principalColumn: "Id",
        onDelete: ReferentialAction.Cascade);
    table.ForeignKey(
        name: "FK_Match_Team_HomeTeamID",
        column: x => x.HomeTeamID,
        principalTable: "Team",
        principalColumn: "Id",
        onDelete: ReferentialAction.Cascade);
});

Set ReferentialAction.NoAction for FK_Match_Team_HomeTeamID.

Upvotes: 2

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