Configuring Entity Framework Core (EF Core) using Fluent API in C# provides fine-grained control over how your entity classes map to database tables and how relationships between entities are defined. Here’s a step-by-step guide on how to configure EF Core using Fluent API:
- Create a DbContext:
Start by creating a class that inherits from `DbContext`, which represents your database context. This class will contain DbSet properties for your entity classes and the configuration using Fluent API.
```csharp
public class YourDbContext : DbContext
{
public DbSet<EntityType> EntityTypes { get; set; }
// DbSet properties for other entities
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
// Fluent API configuration goes here
}
}
```
- Configure Entity Properties:
Inside the `OnModelCreating` method, you can configure entity properties using Fluent API. For example, to specify a maximum length for a string property, you can use the `HasMaxLength` method:
```csharp
modelBuilder.Entity<EntityType>()
.Property(e => e.PropertyName)
.HasMaxLength(50);
```
- Define Primary Keys:
To define primary keys for your entities, use the `HasKey` method:
```csharp
modelBuilder.Entity<EntityType>()
.HasKey(e => e.Id);
```
- Configure Relationships:
Use Fluent API to configure relationships between entities. For instance, to define a one-to-many relationship, use `HasOne` and `WithMany`:
```csharp
modelBuilder.Entity<Author>()
.HasMany(a => a.Books)
.WithOne(b => b.Author);
```
- Specify Table Names:
You can set custom table names using the `ToTable` method:
```csharp
modelBuilder.Entity<EntityType>()
.ToTable("CustomTableName");
```
- Indexes and Constraints:
To define indexes and constraints, use methods like `HasIndex` and `HasCheckConstraint`:
```csharp
modelBuilder.Entity<EntityType>()
.HasIndex(e => e.SomeProperty)
.IsUnique();
modelBuilder.Entity<EntityType>()
.HasCheckConstraint("CheckConstraintName", "SomeProperty > 0");
```
- Seed Data:
You can also seed initial data using Fluent API. Override the `OnModelCreating` method and use the `HasData` method:
```csharp
modelBuilder.Entity<EntityType>()
.HasData(
new EntityType { Id = 1, Property1 = "Value1", Property2 = "Value2" },
// Add more seed data
);
```
By following these steps and utilizing Fluent API in EF Core, you can tailor the database schema and entity behavior to your specific application requirements. It offers a powerful way to configure your data model with precision and flexibility.
