A simple repository library that provides easy way how to store tree hierarchies in Entity framework
There are multiple approaches to storing hierarchical data in SQL tables, each having pros/cons. Materialized path is viable in case you have hierarchy that is ofter read, but rarely written. E.g. product catalogue, categories...
It's not possible to ensure referential integrity by SQL constraints, and it's solely dependent on correct usage of TreeRepository. In case of manual tampering with IMaterializedPathEntity properties outside TreeRepository, it's likely you will end up with inconsistent tree. Therefore always rely on using TreeRepository when changing tree hierarchy.
To ensure consistency, TreeRepository often saves underlying context when manipulating tree hierarchy. To be able to contain these saves as an atomic operation along with your DB updates use transactions.
public class Category : IMaterializedPathEntity<int>
{
/* Props from IMaterializedPathEntity */
public int Id { get; set; }
public string Path { get; set; }
public int Level { get; set; }
public int? ParentId { get; set; }
/* Custom props */
public string Name { get; set; }
}public class MyDbContext : DbContext
{
// Register as DbSet
public DbSet<Category> Categories { get; set; }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
// Apply prepared configuration
modelBuilder.ApplyConfiguration(new MaterializedEntityMapping<Category>());
}
}public void ConfigureServices(IServiceCollection services)
{
services.AddDbContext<MyDbContext>();
// This registers ITreeRepository<Category> for you to use
services.AddTreeRepository<MyDbContext, Category>();
// This adds support for default identifier types (int, string, Guid)
services.AddDefaultIdentifierSerializers();
}or create your own instance
var repo = new TreeRepository<MyDbContext, Category>(
myDbContextInstance,
new IntIdentifierSerializer()
);Gets node by PK
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7
await repository.GetByIdAsync(1)
// will yield node 1Gets parent of queried entity
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7
var node = dbContext.Categories.FindAsync(2);
var parentOfTwo = await repository.GetParentAsync(node);
// will yield node 1Returns nodes from root to queried node in order
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7
var node = dbContext.Categories.FindAsync(10);
var pathFromRootToTen = await repository.GetPathFromRootAsync(node);
// will yield nodes 1,2,6Queries all nodes
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7
repository.Query()
// will yield nodes 1,2,3,4,5,6,7,8,9,10Get all root nodes
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7
repository.QueryRoots()
// will yield node 1Get all nodes that precede queried node (not always in order from root)
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7
var node = dbContext.Categories.FindAsync(5);
var ancestorsOfFive = await repository.QueryAncestors(node).ToListAsync();
// will yield nodes 2, 1Get all nodes which have queries node as ancestor
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7
var node = dbContext.Categories.FindAsync(2);
var descendantsOfTwo = await repository.QueryDescendants(node).ToListAsync();
// will yield nodes 5, 6, 9, 10, 7Gets all sibling nodes (self is not included)
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7
var node = dbContext.Categories.FindAsync(2);
var childrenOfOne = await repository.QuerySiblings(node).ToListAsync();
// will yield nodes 3,4Get all direct children of queried node
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var node = dbContext.Categories.FindAsync(1);
var childrenOfOne = await repository.QueryChildren(node).ToListAsync();
// will yield nodes 2,3,4Updates node and all its descendants, will save the underlying context
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7
var nodeTwo = dbContext.Categories.FindAsync(2);
var nodeThree = dbContext.Categories.FindAsync(3);
await repository.SetParentAsync(nodeTwo, nodeThree);
// Will produce following tree
1───────┐
│ │
3 4
│ │
┌───2───┐ 8
│ │
5 6
│ │
9 10
│
7 ┌───────1───────┐
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var nodeTwo = dbContext.Categories.FindAsync(2);
await repository.SetParentAsync(nodeTwo, null);
// Will produce following trees
┌───2───┐ ┌───1───┐
│ │ │ │
5 6 3 4
│ │ │
9 10 8
│
7 Detaches node from tree, attaching children to detachee's parent.
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7
var nodeTwo = dbContext.Categories.FindAsync(2);
await repository.DetachNodeAsync(nodeTwo);
// Will produce following trees (notice detached 2, and reparented 5,6)
2 ┌─────┬──1──┬─────┐
│ │ │ │
5 6 3 4
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9 10 8
│
7 Deletes node from the tree. Children are parented to parent of deleted node.
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7
var nodeTwo = dbContext.Categories.FindAsync(2);
await repository.DeleteNodeAsync(nodeTwo);
// Will produce following tree
┌─────┬──1──┬─────┐
│ │ │ │
5 6 3 4
│ │ │
9 10 8
│
7 This package supports various types used as primary key, including possibility to add your own. Only condition is it must be struct. It's necessary for the library to be able to serialize/deserialize the identifier types to be used in path strings. Package ships support for int, string & Guid by using AddDefaultIdentifierSerializers() on your ServiceCollection.
If you need to support your own identifier type, all you need to do is implement simple interface IIdentifierSerializer & register it in container.
This is sample implementation of "int" type serializer.
public class IntIdentifierSerializer: IIdentifierSerializer<int>
{
public string SerializeIdentifier(int id) => id.ToString();
public int DeserializeIdentifier(string id) => int.Parse(id);
}
// ...
// And register via
services.AddTransient<IIdentifierSerializer<int>, IntIdentifierSerializer>();Dependency version bump
Microsoft.EntityFrameworkCore 5.0.5 -> 5.0.9
Microsoft.EntityFrameworkCore.Relational 5.0.5 -> 5.0.9
FluentAssertions 5.10.3 -> 6.1.0