How to persist a list of strings with Entity Framework Core?

How to persist a list of strings with Entity Framework Core?

To persist a list of strings with Entity Framework Core, you can use the HasConversion method to convert the list of strings to a single string that can be stored in a database column. Here's an example:

public class MyEntity { public int Id { get; set; } public string Name { get; set; } public List<string> Tags { get; set; } } public class MyContext : DbContext { public DbSet<MyEntity> MyEntities { get; set; } protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity<MyEntity>() .Property(e => e.Tags) .HasConversion( v => string.Join(',', v), v => v.Split(',', StringSplitOptions.RemoveEmptyEntries).ToList()); } }

In this example, we define a MyEntity class with an Id, a Name, and a Tags property that is a list of strings. In the MyContext class, we override the OnModelCreating method to configure the Tags property using the HasConversion method.

The HasConversion method takes two lambdas as arguments: the first lambda converts the list of strings to a single string using the string.Join method and a delimiter (in this case, a comma), and the second lambda converts the single string back to a list of strings using the string.Split method.

With this configuration, the Tags property will be stored as a single string in the database column, separated by commas, and will be automatically converted to and from a list of strings when reading and writing to the database.

Examples

  1. "Entity Framework Core Code-First mapping for a list of strings"

    • Code:
      public class YourEntity { public int Id { get; set; } public List<string> StringList { get; set; } } 
      public class YourDbContext : DbContext { public DbSet<YourEntity> YourEntities { get; set; } protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity<YourEntity>() .Property(e => e.StringList) .HasConversion( v => string.Join(',', v), v => v.Split(',', StringSplitOptions.RemoveEmptyEntries).ToList() ); } }
    • Description: Defines an entity with a list of strings and configures a Code-First migration using HasConversion to store the list as a delimited string in the database.

  2. "Entity Framework Core Value Conversion for a list of strings"

    • Code:
      public class YourEntity { public int Id { get; set; } public List<string> StringList { get; set; } } 
      public class YourDbContext : DbContext { public DbSet<YourEntity> YourEntities { get; set; } protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity<YourEntity>() .Property(e => e.StringList) .HasConversion( v => JsonConvert.SerializeObject(v), v => JsonConvert.DeserializeObject<List<string>>(v) ); } }
    • Description: Uses a Value Conversion to serialize the list of strings to JSON when storing in the database and deserialize it back when reading from the database.

  3. "Entity Framework Core One-to-Many Relationship for a list of strings"

    • Code:
      public class YourEntity { public int Id { get; set; } public List<StringItem> StringItems { get; set; } } public class StringItem { public int Id { get; set; } public string Value { get; set; } } 
      public class YourDbContext : DbContext { public DbSet<YourEntity> YourEntities { get; set; } public DbSet<StringItem> StringItems { get; set; } protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity<YourEntity>() .HasMany(e => e.StringItems) .WithOne() .HasForeignKey(e => e.YourEntityId); } }
    • Description: Establishes a one-to-many relationship by creating a separate entity (StringItem) for each string in the list and linking them with a foreign key.

  4. "Entity Framework Core Many-to-Many Relationship for a list of strings"

    • Code:
      public class YourEntity { public int Id { get; set; } public List<StringItem> StringItems { get; set; } } public class StringItem { public int Id { get; set; } public string Value { get; set; } public List<YourEntity> YourEntities { get; set; } } 
      public class YourDbContext : DbContext { public DbSet<YourEntity> YourEntities { get; set; } public DbSet<StringItem> StringItems { get; set; } protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity<YourEntity>() .HasMany(e => e.StringItems) .WithMany(s => s.YourEntities) .UsingEntity(j => j.ToTable("YourEntityStringItem")); } }
    • Description: Creates a many-to-many relationship by introducing an intermediate table (YourEntityStringItem) to link the YourEntity and StringItem entities.

  5. "Entity Framework Core Table-Valued Parameter for a list of strings"

    • Code:
      public class YourEntity { public int Id { get; set; } public List<StringItem> StringItems { get; set; } } [Owned] public class StringItem { public string Value { get; set; } } 
      public class YourDbContext : DbContext { public DbSet<YourEntity> YourEntities { get; set; } protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity<YourEntity>() .OwnsMany(e => e.StringItems, a => { a.ToTable("YourEntityStringItem"); a.Property<string>("Value"); }); } }
    • Description: Uses the [Owned] attribute to create a complex type (StringItem) and represents the list of strings as a table-valued parameter.

  6. "Entity Framework Core Value Conversion for an array of strings"

    • Code:
      public class YourEntity { public int Id { get; set; } public string[] StringArray { get; set; } } 
      public class YourDbContext : DbContext { public DbSet<YourEntity> YourEntities { get; set; } protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity<YourEntity>() .Property(e => e.StringArray) .HasConversion( v => string.Join(',', v), v => v.Split(',', StringSplitOptions.RemoveEmptyEntries) ); } }
    • Description: Adapts the Value Conversion approach to work with an array of strings.

  7. "Entity Framework Core Separate Table for a list of strings"

    • Code:
      public class StringItem { public int Id { get; set; } public string Value { get; set; } } 
      public class YourEntity { public int Id { get; set; } } 
      public class YourDbContext : DbContext { public DbSet<YourEntity> YourEntities { get; set; } public DbSet<StringItem> StringItems { get; set; } protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity<YourEntity>() .HasMany(e => e.StringItems) .WithMany() .UsingEntity(j => j.ToTable("YourEntityStringItem")); } }
    • Description: Establishes a many-to-many relationship with a separate table (YourEntityStringItem) to store the list of strings.

  8. "Entity Framework Core JSON column for a list of strings"

    • Code:
      public class YourEntity { public int Id { get; set; } public List<string> StringList { get; set; } } 
      public class YourDbContext : DbContext { public DbSet<YourEntity> YourEntities { get; set; } protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity<YourEntity>() .Property(e => e.StringList) .HasColumnType("jsonb"); } }
    • Description: Configures the property to be stored as a JSON column in databases that support JSON types (e.g., PostgreSQL with jsonb).

  9. "Entity Framework Core String Interpolation for a list of strings"

    • Code:
      public class YourEntity { public int Id { get; set; } public string StringList { get; set; } } 
      public class YourDbContext : DbContext { public DbSet<YourEntity> YourEntities { get; set; } protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity<YourEntity>() .Property(e => e.StringList) .HasConversion( v => string.Join(',', v), v => v.Split(',', StringSplitOptions.RemoveEmptyEntries).ToList() ); } }
    • Description: Applies the String Interpolation technique to store a list of strings as a delimited string in the database.

  10. "Entity Framework Core Table-Valued Function for a list of strings"

    • Code:
      public class YourEntity { public int Id { get; set; } public List<StringItem> StringItems { get; set; } } [Keyless] public class StringItem { public string Value { get; set; } } 
      public class YourDbContext : DbContext { public DbSet<YourEntity> YourEntities { get; set; } protected override void OnModelCreating(ModelBuilder modelBuilder) { modelBuilder.Entity<YourEntity>() .ToFunction("YourTableValuedFunction") .HasMany(e => e.StringItems) .HasNoKey(); } }
    • Description: Maps to a table-valued function (YourTableValuedFunction) to handle a list of strings as an output.

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