Struggling with mocking frameworks for unit tests, I find it easier to execute queries as strings rather than lambda expressions within my projects. This has led me to consider modifying my IDatabase interface:
Interface IDatabase
{
IEnumerable<User> Find(string query);
}
Although many of my queries are already written using expressions, I have devised a method to convert these expressions to JSON objects:
using MongoDB.Driver;
using System.Linq.Expressions;
class Program
{
// Sample user collection stored in database
class User
{
public string _id { get; set; }
public string Name { get; set; }
public DateTime DateCreated { get; set; }
}
// Main method
public static void Main()
{
var json = ExpressionToJson<User>(x => x.Name.Contains("Tono") && x.DateCreated < DateTime.UtcNow);
Console.WriteLine(json);
}
/// <summary>
/// Converts an expression to a JSON string
/// </summary>
public static string ExpressionToJson<T>(Expression<Func<T, bool>> filter)
{
MongoClient MongoClient = new MongoClient();
var db1 = MongoClient.GetDatabase("DoesNotMatter");
var collection = db1.GetCollection<T>("DoesNotMatter");
var query = collection.Find(filter);
var json = query.ToString();
if (string.IsNullOrEmpty(json))
return "{}";
if (json.StartsWith("find("))
return json.Substring(5, json.Length - 6);
throw new NotImplementedException("Has the serializer changed?");
}
}
This method can simplify converting expressions like
x => x.Name.Contains("Tono") && x.DateCreated < DateTime.UtcNow
to JSON format.
{ "Name" : /Tono/s, "DateCreated" : { "$lt" : ISODate("2022-01-21T01:24:38.628Z") } }
I am looking for ways to streamline the ExpressionToJson method to avoid unnecessary instantiation of MongoClient, Database, and
IMongoCollection<TDocument>