EF Core Fluent API HasData adding delete data on subsequent migration - entity-framework-core

Question

I am using HasData to seed data and it is creating insert data migration script right but with the subsequent migrations it is adding delete migrations without any further changes.
Entities
Country
public class Country : BaseEntity
{
public string CountryName { get; set; }
}
County
public class County : BaseEntity
{
public string CountyName { get;set; }
public int CountryId { get;set; }
public Country Country { get; set; }
}
BaseEntity
public class BaseEntity
{
public int Id { get; set; }
public Guid ApplicationUserId { get; set; }
}
Configurations
public class CountyConfiguration : BaseEntityConfiguration<County>
{
private const string TABLE_NAME = "Counties";
public CountyConfiguration() : base(TABLE_NAME)
{
}
public override void Configure(EntityTypeBuilder<County> entity)
{
base.Configure(entity);
entity.Property(c => c.CountyName).IsRequired().HasMaxLength(100);
entity.HasIndex(c => c.CountryId).IsUnique(false);
entity.HasIndex(c => new {c.CountyName, c.CountryId }).IsUnique();
entity.HasOne(c => c.Country).WithOne().OnDelete(DeleteBehavior.Cascade);
entity.Ignore(c => c.ApplicationUserId);
entity.HasData(
new County { Id = 1, CountryId = 1, CountyName = "Antrim"},
new County { Id = 2, CountryId = 1, CountyName = "Carlow"},
new County { Id = 3, CountryId = 1, CountyName = "Cavan"},
new County { Id = 4, CountryId = 1, CountyName = "Clare"},
new County { Id = 5, CountryId = 1, CountyName = "Cork"},
new County { Id = 6, CountryId = 1, CountyName = "Derry (Londonderry)"},
new County { Id = 7, CountryId = 1, CountyName = "Donegal"},
new County { Id = 8, CountryId = 1, CountyName = "Dublin"},
new County { Id = 9, CountryId = 1, CountyName = "Galway"},
new County { Id = 10, CountryId = 1, CountyName = "Kerry"},
new County { Id = 11, CountryId = 1, CountyName = "Kildare"},
new County { Id = 12, CountryId = 1, CountyName = "Kilkenny"},
new County { Id = 13, CountryId = 1, CountyName = "Laois (Queens)"},
new County { Id = 14, CountryId = 1, CountyName = "Leitrim"},
new County { Id = 15, CountryId = 1, CountyName = "Limerick"},
new County { Id = 16, CountryId = 1, CountyName = "Longford"},
new County { Id = 17, CountryId = 1, CountyName = "Louth"},
new County { Id = 18, CountryId = 1, CountyName = "Mayo"},
new County { Id = 19, CountryId = 1, CountyName = "Meath"},
new County { Id = 20, CountryId = 1, CountyName = "Monaghan"},
new County { Id = 21, CountryId = 1, CountyName = "Offaly (Kings)"},
new County { Id = 22, CountryId = 1, CountyName = "Roscommon"},
new County { Id = 23, CountryId = 1, CountyName = "Sligo"},
new County { Id = 24, CountryId = 1, CountyName = "Tipperary"},
new County { Id = 25, CountryId = 1, CountyName = "Waterford"},
new County { Id = 26, CountryId = 1, CountyName = "Westmeath"},
new County { Id = 27, CountryId = 1, CountyName = "Wexford"},
new County { Id = 28, CountryId = 1, CountyName = "Wicklow"}
);
}
}
Generated Migration1:
public partial class County : Migration
{
protected override void Up(MigrationBuilder migrationBuilder)
{
migrationBuilder.CreateTable(
name: "Counties",
columns: table => new
{
Id = table.Column<int>(type: "int", nullable: false)
.Annotation("SqlServer:Identity", "1, 1"),
CountyName = table.Column<string>(type: "nvarchar(100)", maxLength: 100, nullable: false),
CountryId = table.Column<int>(type: "int", nullable: false)
},
constraints: table =>
{
table.PrimaryKey("Pk_Counties_Id", x => x.Id);
table.ForeignKey(
name: "FK_Counties_Countries_CountryId",
column: x => x.CountryId,
principalTable: "Countries",
principalColumn: "Id",
onDelete: ReferentialAction.Cascade);
});
migrationBuilder.InsertData(
table: "Counties",
columns: new[] { "Id", "CountryId", "CountyName" },
values: new object[,]
{
{ 3, 1, "Cavan" },
{ 26, 1, "Westmeath" },
{ 25, 1, "Waterford" },
{ 24, 1, "Tipperary" },
{ 23, 1, "Sligo" },
{ 22, 1, "Roscommon" },
{ 21, 1, "Offaly (Kings)" },
{ 20, 1, "Monaghan" },
{ 19, 1, "Meath" },
{ 18, 1, "Mayo" },
{ 17, 1, "Louth" },
{ 16, 1, "Longford" },
{ 27, 1, "Wexford" },
{ 15, 1, "Limerick" },
{ 13, 1, "Laois (Queens)" },
{ 12, 1, "Kilkenny" },
{ 11, 1, "Kildare" },
{ 10, 1, "Kerry" },
{ 9, 1, "Galway" },
{ 8, 1, "Dublin" },
{ 7, 1, "Donegal" },
{ 6, 1, "Derry (Londonderry)" },
{ 5, 1, "Cork" },
{ 4, 1, "Clare" },
{ 2, 1, "Carlow" },
{ 14, 1, "Leitrim" },
{ 28, 1, "Wicklow" }
});
migrationBuilder.CreateIndex(
name: "IX_Counties_CountryId",
table: "Counties",
column: "CountryId");
migrationBuilder.CreateIndex(
name: "IX_Counties_CountyName_CountryId",
table: "Counties",
columns: new[] { "CountyName", "CountryId" },
unique: true);
}
protected override void Down(MigrationBuilder migrationBuilder)
{
migrationBuilder.DropTable(
name: "Counties");
}
}
Next Migration 2: (Without any changes)
public partial class Empty : Migration
{
protected override void Up(MigrationBuilder migrationBuilder)
{
migrationBuilder.DeleteData(
table: "Counties",
keyColumn: "Id",
keyValue: 1);
}
protected override void Down(MigrationBuilder migrationBuilder)
{
migrationBuilder.DeleteData(
table: "Counties",
keyColumn: "Id",
keyValue: 1);
migrationBuilder.InsertData(
table: "Counties",
columns: new[] { "Id", "CountryId", "CountyName" },
values: new object[] { 1, 1, "Antrim" });
}
}
Not sure, why it is adding migrationBuilder.DeleteData delete script?

Answer 1

Here
entity.HasOne(c => c.Country).WithOne().OnDelete(DeleteBehavior.Cascade);
with WithOne() you are basically telling EF that the County.CountryId must be unique (because the only difference between one-to-one and one-to-many in relational databases is the unique constraint (index) for the FK column(s)).
However, before that you are telling EF the opposite
entity.HasIndex(c => c.CountryId).IsUnique(false);
This sequence of conflicting configurations somehow confuses EF and it starts doing strange things.
While this could be considered their bug, at the end the problem is in your code, since apparently you don't want one-to-one relationship. So correct that by replacing HasOne with HasMany
entity.HasOne(c => c.Country).WithMany().OnDelete(DeleteBehavior.Cascade);
or completely remove it since all it does is the same as the default EF Core conventions.
Once you do that, you could also remove the HasIndex configuration since it is also the default by EF Core FK index convention.