Question

我正在尝试使用两个引用另一个模型的模型。

我已经研究过这个错误，但是看过有关以前.Net Core版本的建议。

以下是模型

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; }
}

运行迁移后，我收到此错误：

介绍FOREIGN KEY约束＆＃39; FK_Matches_Teams_AwayTeamID＆＃39;在桌子上＆＃39;比赛＆＃39;可能会导致循环或多个级联路径。指定ON DELETE NO ACTION或ON UPDATE NO ACTION，或修改其他FOREIGN KEY约束。

Answer 1

当您运行Add-Migration时，它将生成类似于以下代码的迁移文件。

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);
});

为ReferentialAction.NoAction设置FK_Match_Team_HomeTeamID。

Answer 2

所以..解决方案很简单。

我将外键ID设为可空。我不确定是否可以同时使用nullable＆＃39;

请参阅以下代码：

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; }

}

实体框架核心2 - 外键约束

2 个答案: