EF Classic - LINQ Dynamic - Immediate Methods - FirstOrDefault

CSharp · Console

/Program.cs

// Entity Framework Classic
// Doc: https://entityframework-classic.net/linq-dynamic

// @nuget: Z.EntityFramework.Classic
// @nuget: Newtonsoft.Json

using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Linq.Expressions;  
using Newtonsoft.Json;
using Z.Expressions;

public class Program
{
	public static void Main()
	{
		GenerateData();
		
		var json = @"
[
	{
	  'Method': 'FirstOrDefault',
	  'Field': 'Name',
	  'Operation': '==',
	  'Value': '""Customer_A""',
	},
	{
	  'Method': 'FirstOrDefault',
	  'Expression': 'Description.Contains(""ZZZ Projects"")',
	} 
]
";
		var queryCriterias = JsonConvert.DeserializeObject<List<Criteria>>(json);

		using (var context = new EntityContext())
		{		
			var query = context.Customers.AsQueryable();
			
			foreach(var qc in queryCriterias)
			{
				if(qc.Method == "FirstOrDefault") 
				{
					if(!string.IsNullOrEmpty(qc.Expression))
					{
						var customer = query.FirstOrDefault(x => "x." + qc.Expression);
						
						FiddleHelper.WriteTable("Expression : x." + qc.Expression, new List<Customer>() {customer});
					}
					else
					{
						var expression = "x.[Field] [Operation] [Value]"
						.Replace("[Field]", qc.Field)
						.Replace("[Operation]", qc.Operation)
						.Replace("[Value]", qc.Value);
						
					 	var customer = query.FirstOrDefault(x => expression);
						
						FiddleHelper.WriteTable("Expression : " + expression, new List<Customer>() {customer});
					}
				}
			}
			
		}
	}

	public static void GenerateData()
	{
		using (var context = new EntityContext())
		{
			context.Customers.Add(new Customer() { Name = "Customer_A", Description = "ZZZ Projects"});
			context.Customers.Add(new Customer() { Name = "Customer_A", Description = "Description"});			
			context.Customers.Add(new Customer() { Name = "Customer_B", Description = "Description"});
			
			context.SaveChanges();	
		}
	}

	public class EntityContext : DbContext
	{		
		public EntityContext() : base(FiddleHelper.GetConnectionStringSqlServer())
		{		
		}

		public DbSet<Customer> Customers { get; set; }
	}
	
	public class Customer
	{
		public int CustomerID { get; set; }
		public string Name { get; set; }
		public string Description { get; set; }
	}
	
	public class Criteria
	{
		public string Method { get; set; }
		public string Field { get; set; }
		public string Operation { get; set; }
		public string Value { get; set; }
		public string Expression { get; set; }
	}
}