Save Entity Framework Linq Query to database

Question

I was wondering if we can convert a Linq Query on the Entity Framework and save the query to the database by converting it to an Expression Tree and Serializing. Can someone

Answer 1

You could turn the query into a string and then save the string.

This is from an answer by Nick Berardi:

var result = from x in appEntities
         where x.id = 32
         select x;

var sql = ((System.Data.Objects.ObjectQuery)result).ToTraceString();

The sql generated by the query could be stored and re-used.

Answer 2

Use Sprint.Filter.OData. It converts a Func<T,bool> into string and back to code.

Sample:

public class TestSprintOData
{
    public static void Run()
    {
        // Parse a Func into string
        var query = Filter.Serialize<User>(u => u.IsActive && u.Email.Contains("@gmail.com"));

        // It'll generate the string "IsActive and substringof('@gmail.com', Email)"

        // Convert back to Expression, perhaps on server
        var query2 = Filter.Deserialize<User>(query);

        // Compiles to Func, so you can use as delegate to Where
        var f = query2.Compile();

        var list = new List<User>
        {
            new User{Name="Johnny", IsActive = true, Email = "johnny@gmail.com"},
            new User{Name="abc", IsActive = false, Email = ""},
            new User{Name="dude", IsActive=true, Email = "dude@gmail.com"}
        };

        var result = list.Where(f);            
    }
}

class User
{
    public string Name;
    public string Phone;
    public string Login;
    public string Email;
    public bool IsActive;
}

You can also use it as a Nuget Package

Answer 3

You may want to consider using Entity SQL rather than LINQ in this case. Entity SQL is a string query that works against your EF conceptual model rather than directly against the database.

Answer 4

i released a library for that purpose just yesterday. Serialize.Linq. It serializes linq expressions to xml, json or binary.

using System.Linq.Expressions
using Serialize.Linq.Extensions;

Expression<Func<Person, bool>> query = p => p.LastName == "Miller" 
    && p.FirstName.StartsWith("M");

Console.WriteLine(query.ToJson());
Console.WriteLine(query.ToXml());