This is a collection of extension methods for the Neo4j.Driver.
The aim is to make it a bit simpler to use, it doesn't cover all use cases at the moment, and is a work in progress that I'll update as and when new cases arrive.
This is NetStandard2.1 to allow the use of IAsyncEnumerable and as such - can't be
used in any lower version.
Available on Nuget
For the below examples, the Movie class looks like:
public class Movie
{
[Neo4jProperty(Name = "title")]
public string Title { get; set; }
[Neo4jProperty(Name = "released")]
public long? Released { get; set; }
[Neo4jProperty(Name = "tagline")]
public string Tagline { get; set; }
public static string Labels => nameof(Movie);
}
If you use the Neo4j.Driver to access your data, you have to write code like this:
var session = _driver.AsyncSession();
var results = await session.ReadTransactionAsync(async x =>
{
var cursor = await x.RunAsync($"MATCH (m:{Movie.Labels}) WHERE m.title = $title RETURN m", new { title });
var fetched = await cursor.FetchAsync();
while (fetched)
{
var node = cursor.Current["m"].As<INode>();
var movie = new Movie
{
Title = node.Properties.ContainsKey("title") ? node.Properties["title"].As<string>() : null,
Tagline = node.Properties.ContainsKey("tagline") ? node.Properties["tagline"].As<string>() : null,
Released = node.Properties.ContainsKey("released") ? node.Properties["released"].As<int?>() : null
};
return movie;
}
return null;
});
return results;
There is a lot of boiler plate code around there, and some you'll want to keep, but the aim of this project is to make that a bit simpler to use. The examples below will take the above code and show how you can use the extensions to make it easier to read.
The first thing we can do is make the getting of values better, so, let's take the Properties getters:
Title = node.Properties.ContainsKey("title") ? node.Properties["title"].As<string>() : null,
and replace with:
Title = node.GetValue<string>("title"),
or
Title = node.GetValueStrict<string>("title"),
GetValue<T> will return the value from the INode, or a default, so for string the default is null for int the default is 0.
GetValueStrict<T> will return the value, or throw a KeyNotFoundException exception if the value isn't there. So choose whichever makes
most sense in your code.
Issues - This hasn't been tested with IEnumerable properties, at the moment, just primitives.
We can take the entire Movie creation code:
var movie = new Movie
{
Title = node.Properties.ContainsKey("title") ? node.Properties["title"].As<string>() : null,
Tagline = node.Properties.ContainsKey("tagline") ? node.Properties["tagline"].As<string>() : null,
Released = node.Properties.ContainsKey("released") ? node.Properties["released"].As<int?>() : null
};
and change it to:
var movie = node.ToObject<Movie>();
Issues - As with GetValue<T> this only copes with primitive properties at the moment!
This allows you to decorate your class' properties with attributes to let the ToObject<T> method know how you want to read your data.
To use a different name in the database to your classes, use the Name property:
[Neo4jProperty(Name = "title")]
public string Title { get; set; }
To ignore a property, so no attempt is made to read it, use the Ignore property:
[Neo4jProperty(Ignore = true)]
public string Title { get; set; }