DynamicFilter

DynamicFilter allows to use essential linq filtering methods in web api apps.

All operations were tested against EF Core and PostgreSql.

Usage

Model:

class Product
{
    public Guid Id { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
    public bool IsInStock { get; set; }
    public bool IsForSale { get; set; }
    public DateTime ExpireDate { get; set; }
}

Controller:

[Route("[controller]")]
public class ProductsController : ControllerBase
{
    private readonly AppDbContext _dbcontext;

    public ProductsController(AppDbContext dbcontext)
    {
        _dbcontext = dbcontext;
    }

    [HttpPost("filter")]
    public IActionResult GetFiltered([FromBody] Operation[] filter)
    {
        return Ok(_dbcontext.Set<Product>().ApplyDynamicFilter(filter));
    }
}

Filter:

[
	{
		"name": "where",
		"arguments": 
                {
			"conditions": 
			[
				{
					"field": "Name",
					"operator": "Contains",
					"value": ["Snickers"]
				},
				{
					"logic": "And",
					"field": "IsForSale",
					"operator": "Equals",
					"value": ["true"]
				}
			],
			"groups": []
		}
	},
	{
		"name": "distinct"
	},
	{
		"name": "orderBy",
		"arguments": "ExpireDate"
	},
	{
		"name": "orderByDescending",
		"arguments": "Price"
	},
	{
		"name": "thenBy",
		"arguments": "IsInStock"
	},
	{
		"name": "thenByDescending",
		"arguments": "IsForSale"
	},
        {
		"name": "skip",
		"arguments": 1
	},
	{
		"name": "take",
		"arguments": 2
	},
	{
		"name": "select",
		"arguments": ["Id", "Name"]
	}
]

Under the hood filter transforms into call

_dbcontext.Set<Product>()
    .Where(x => x.Name.Contains("Snickers") && x.IsForSale)
    .Distinct()
    .OrderBy(x => x.ExpireDate)
    .OrderByDescending(x => x.Price)
    .ThenBy(x => x.IsInStock)
    .ThenByDescending(x => x.IsForSale)
    .Skip(1)
    .Take(2)
    .Select(x => new Dictionary<string, object>()
    {
        {"Id", x.Id},
        {"Name", x.Name}
    });

Such implementation of Select was made due to the limitations of anonymous types and should be used as the last operation and only to reduce the final number of properties to be fetched from the database.

At this point following operators are available to use in Where predicate:

    Equals
    NotEqual
    Any
    Greater
    GreaterOrEqual
    Less
    LessOrEqual
    Exists
    NotExists
    StartsWith
    EndsWith
    Contains
    NotContains

Examples

Advanced filtering

.Where(x => ((x.Name.EndsWith("Mars") || ["Snickers", "Mars"].Contains(x.Name)) && x.ExpireDate >= DateTime.UtcNow) && (x.IsForSale || x.IsInStock))

[
	{
		"name": "where",
		"arguments": 
		{
			"conditions": 
			[
				{
					"field": "Name",
					"operator": "EndsWith",
					"value": ["Mars"]
				},
				{
					"logic": "Or",
					"field": "Name",
					"operator": "Any",
					"value": ["Snickers", "Mars"]
				},
				{
					"logic": "And",
					"field": "ExpireDate",
					"operator": "GreaterOrEqual",
					"value": ["2023-02-13 17:56:19Z"]
				},
				{
					"logic": "And",
					"field": "IsForSale",
					"operator": "Equals",
					"value": ["true"]
				},
				{
					"logic": "Or",
					"field": "IsInStock",
					"operator": "Equals",
					"value": ["true"]
				}
			],
			"groups": 
			[
				{
					"start": 1,
					"end": 2,
					"level": 1
				},
				{
					"start": 1,
					"end": 3,
					"level": 2
				},
				{
					"start": 4,
					"end": 5,
					"level": 2
				}
			]
		}
	}
]

Fetching specific field values

.Select(x => x.Price)
.Distinct()
.OrderBy(x => x)

[
	{
		"name": "select",
		"arguments": "Price"
	},
	{
		"name": "distinct"
	},
	{
		"name": "orderBy"
	}
]