├── .gitattributes ├── .gitignore ├── DatabaseTest ├── DatabaseTest.csproj ├── Program.cs ├── TransactionContext.cs └── databaseRules.json ├── ExpressionGenerator.sln ├── ExpressionGenerator ├── ExpressionGenerator.csproj ├── JsonExpressionParser.cs ├── Program.cs ├── Transaction.cs └── rules.json ├── LICENSE └── README.md /.gitattributes: -------------------------------------------------------------------------------- 1 | ############################################################################### 2 | # Set default behavior to automatically normalize line endings. 3 | ############################################################################### 4 | * text=auto 5 | 6 | ############################################################################### 7 | # Set default behavior for command prompt diff. 8 | # 9 | # This is need for earlier builds of msysgit that does not have it on by 10 | # default for csharp files. 11 | # Note: This is only used by command line 12 | ############################################################################### 13 | #*.cs diff=csharp 14 | 15 | ############################################################################### 16 | # Set the merge driver for project and solution files 17 | # 18 | # Merging from the command prompt will add diff markers to the files if there 19 | # are conflicts (Merging from VS is not affected by the settings below, in VS 20 | # the diff markers are never inserted). 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2 | using ExpressionGenerator; 3 | using Microsoft.Extensions.Logging; 4 | using Microsoft.Extensions.Logging.Console; 5 | using System; 6 | using System.Text.Json; 7 | using System.IO; 8 | using System.Linq; 9 | using System.Linq.Expressions; 10 | using System.Threading.Tasks; 11 | 12 | namespace DatabaseTest 13 | { 14 | class Program 15 | { 16 | public static readonly ILoggerFactory loggerFactory = 17 | LoggerFactory.Create(builder => 18 | { 19 | builder.AddFilter("Microsoft.EntityFrameworkCore.Database.Command", 20 | LogLevel.Information) 21 | .AddConsole(); 22 | }); 23 | 24 | static async Task Main(string[] args) 25 | { 26 | Console.WriteLine("Creating and seeding database..."); 27 | var options = new DbContextOptionsBuilder() 28 | .UseSqlite("Data Source=transactions.db").Options; 29 | using (var context = new TransactionContext(options)) 30 | { 31 | await context.Database.EnsureDeletedAsync(); 32 | await context.Database.EnsureCreatedAsync(); 33 | context.DbTransactions.AddRange(Transaction.GetList(1000)); 34 | await context.SaveChangesAsync(); 35 | } 36 | 37 | var optionsWithLog = new DbContextOptionsBuilder() 38 | .UseSqlite("Data Source=transactions.db") 39 | .UseLoggerFactory(loggerFactory).Options; 40 | 41 | using (var context = new TransactionContext(optionsWithLog)) 42 | { 43 | var count = await context.DbTransactions.CountAsync(); 44 | Console.WriteLine($"Verified insert count: {count}."); 45 | Console.WriteLine("Parsing expression..."); 46 | var parser = new JsonExpressionParser(); 47 | var predicate = parser.ParseExpressionOf( 48 | JsonDocument.Parse( 49 | await File.ReadAllTextAsync("databaseRules.json"))); 50 | Console.WriteLine("Retrieving from database..."); 51 | var query = context.DbTransactions.Where(predicate) 52 | .OrderBy(t => t.Id); 53 | var results = await query.ToListAsync(); 54 | Console.WriteLine($"Retrieved {results.Count}"); 55 | Console.WriteLine("Sample:"); 56 | Console.WriteLine(results[0]); 57 | } 58 | } 59 | } 60 | } 61 | -------------------------------------------------------------------------------- /DatabaseTest/TransactionContext.cs: -------------------------------------------------------------------------------- 1 | using Microsoft.EntityFrameworkCore; 2 | using ExpressionGenerator; 3 | 4 | namespace DatabaseTest 5 | { 6 | public class TransactionContext : DbContext 7 | { 8 | public TransactionContext(DbContextOptions options) 9 | : base(options) { } 10 | 11 | public DbSet DbTransactions { get; set; } 12 | } 13 | } 14 | -------------------------------------------------------------------------------- /DatabaseTest/databaseRules.json: -------------------------------------------------------------------------------- 1 | { 2 | "condition": "and", 3 | "rules": [ 4 | { 5 | "label": "Category", 6 | "field": "Category", 7 | "operator": "in", 8 | "type": "string", 9 | "value": [ 10 | "Clothing" 11 | ] 12 | }, 13 | { 14 | "condition": "or", 15 | "rules": [ 16 | { 17 | "label": "TransactionType", 18 | "field": "TransactionType", 19 | "operator": "equal", 20 | "type": "boolean", 21 | "value": "income" 22 | }, 23 | { 24 | "label": "PaymentMode", 25 | "field": "PaymentMode", 26 | "operator": "equal", 27 | "type": "string", 28 | "value": "Credit" 29 | } 30 | ] 31 | }, 32 | { 33 | "label": "Amount", 34 | "field": "Amount", 35 | "operator": "equal", 36 | "type": "number", 37 | "value": 10 38 | } 39 | ] 40 | } -------------------------------------------------------------------------------- /ExpressionGenerator.sln: -------------------------------------------------------------------------------- 1 |  2 | Microsoft Visual Studio Solution File, Format Version 12.00 3 | # Visual Studio Version 16 4 | VisualStudioVersion = 16.0.30105.148 5 | MinimumVisualStudioVersion = 10.0.40219.1 6 | Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "ExpressionGenerator", "ExpressionGenerator\ExpressionGenerator.csproj", "{D04773D4-8E39-4D6C-B6C7-C8ADCBD35653}" 7 | EndProject 8 | Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "DatabaseTest", "DatabaseTest\DatabaseTest.csproj", "{ED397E55-0EDB-48AF-8C72-E72D123F7031}" 9 | EndProject 10 | Global 11 | GlobalSection(SolutionConfigurationPlatforms) = preSolution 12 | Debug|Any CPU = Debug|Any CPU 13 | Release|Any CPU = Release|Any CPU 14 | EndGlobalSection 15 | GlobalSection(ProjectConfigurationPlatforms) = postSolution 16 | {D04773D4-8E39-4D6C-B6C7-C8ADCBD35653}.Debug|Any CPU.ActiveCfg = Debug|Any CPU 17 | {D04773D4-8E39-4D6C-B6C7-C8ADCBD35653}.Debug|Any CPU.Build.0 = Debug|Any CPU 18 | {D04773D4-8E39-4D6C-B6C7-C8ADCBD35653}.Release|Any CPU.ActiveCfg = Release|Any CPU 19 | {D04773D4-8E39-4D6C-B6C7-C8ADCBD35653}.Release|Any CPU.Build.0 = Release|Any CPU 20 | {ED397E55-0EDB-48AF-8C72-E72D123F7031}.Debug|Any CPU.ActiveCfg = Debug|Any CPU 21 | {ED397E55-0EDB-48AF-8C72-E72D123F7031}.Debug|Any CPU.Build.0 = Debug|Any CPU 22 | {ED397E55-0EDB-48AF-8C72-E72D123F7031}.Release|Any CPU.ActiveCfg = Release|Any CPU 23 | {ED397E55-0EDB-48AF-8C72-E72D123F7031}.Release|Any CPU.Build.0 = Release|Any CPU 24 | EndGlobalSection 25 | GlobalSection(SolutionProperties) = preSolution 26 | HideSolutionNode = FALSE 27 | EndGlobalSection 28 | GlobalSection(ExtensibilityGlobals) = postSolution 29 | SolutionGuid = {7FB97000-A94F-4B05-ACB1-8AE3A765AF67} 30 | EndGlobalSection 31 | EndGlobal 32 | -------------------------------------------------------------------------------- /ExpressionGenerator/ExpressionGenerator.csproj: -------------------------------------------------------------------------------- 1 | 2 | 3 | 4 | Exe 5 | net5.0 6 | 7 | 8 | 9 | 10 | PreserveNewest 11 | 12 | 13 | 14 | 15 | -------------------------------------------------------------------------------- /ExpressionGenerator/JsonExpressionParser.cs: -------------------------------------------------------------------------------- 1 | using System; 2 | using System.Linq; 3 | using System.Linq.Expressions; 4 | using System.Reflection; 5 | using System.Text.Json; 6 | 7 | namespace ExpressionGenerator 8 | { 9 | public class JsonExpressionParser 10 | { 11 | private const string StringStr = "string"; 12 | 13 | private readonly string BooleanStr = nameof(Boolean).ToLower(); 14 | private readonly string Number = nameof(Number).ToLower(); 15 | private readonly string In = nameof(In).ToLower(); 16 | private readonly string And = nameof(And).ToLower(); 17 | 18 | private readonly MethodInfo MethodContains = typeof(Enumerable).GetMethods( 19 | BindingFlags.Static | BindingFlags.Public) 20 | .Single(m => m.Name == nameof(Enumerable.Contains) 21 | && m.GetParameters().Length == 2); 22 | 23 | private delegate Expression Binder(Expression left, Expression right); 24 | 25 | private Expression ParseTree( 26 | JsonElement condition, 27 | ParameterExpression parm) 28 | { 29 | Expression left = null; 30 | var gate = condition.GetProperty(nameof(condition)).GetString(); 31 | 32 | JsonElement rules = condition.GetProperty(nameof(rules)); 33 | 34 | Binder binder = gate == And ? (Binder)Expression.And : Expression.Or; 35 | 36 | Expression bind(Expression left, Expression right) => 37 | left == null ? right : binder(left, right); 38 | 39 | foreach (var rule in rules.EnumerateArray()) 40 | { 41 | if (rule.TryGetProperty(nameof(condition), out JsonElement check)) 42 | { 43 | var right = ParseTree(rule, parm); 44 | left = bind(left, right); 45 | continue; 46 | } 47 | 48 | string @operator = rule.GetProperty(nameof(@operator)).GetString(); 49 | string type = rule.GetProperty(nameof(type)).GetString(); 50 | string field = rule.GetProperty(nameof(field)).GetString(); 51 | 52 | JsonElement value = rule.GetProperty(nameof(value)); 53 | 54 | var property = Expression.Property(parm, field); 55 | 56 | if (@operator == In) 57 | { 58 | var contains = MethodContains.MakeGenericMethod(typeof(string)); 59 | object val = value.EnumerateArray().Select(e => e.GetString()) 60 | .ToList(); 61 | var right = Expression.Call( 62 | contains, 63 | Expression.Constant(val), 64 | property); 65 | left = bind(left, right); 66 | } 67 | else 68 | { 69 | object val = (type == StringStr || type == BooleanStr) ? 70 | (object)value.GetString() : value.GetDecimal(); 71 | var toCompare = Expression.Constant(val); 72 | var right = Expression.Equal(property, toCompare); 73 | left = bind(left, right); 74 | } 75 | } 76 | 77 | return left; 78 | } 79 | 80 | public Expression> ParseExpressionOf(JsonDocument doc) 81 | { 82 | var itemExpression = Expression.Parameter(typeof(T)); 83 | var conditions = ParseTree(doc.RootElement, itemExpression); 84 | if (conditions.CanReduce) 85 | { 86 | conditions = conditions.ReduceAndCheck(); 87 | } 88 | 89 | Console.WriteLine(conditions.ToString()); 90 | 91 | var query = Expression.Lambda>(conditions, itemExpression); 92 | return query; 93 | } 94 | 95 | public Func ParsePredicateOf(JsonDocument doc) 96 | { 97 | var query = ParseExpressionOf(doc); 98 | return query.Compile(); 99 | } 100 | } 101 | } -------------------------------------------------------------------------------- /ExpressionGenerator/Program.cs: -------------------------------------------------------------------------------- 1 | using System; 2 | using System.IO; 3 | using System.Linq; 4 | using System.Text.Json; 5 | 6 | namespace ExpressionGenerator 7 | { 8 | class Program 9 | { 10 | static void Main(string[] args) 11 | { 12 | static void writeAndWait(string str) 13 | { 14 | Console.WriteLine(str); 15 | Console.ReadLine(); 16 | } 17 | 18 | var jsonStr = File.ReadAllText("rules.json"); 19 | var jsonDocument = JsonDocument.Parse(jsonStr); 20 | 21 | var jsonExpressionParser = new JsonExpressionParser(); 22 | var predicate = jsonExpressionParser 23 | .ParsePredicateOf(jsonDocument); 24 | 25 | var transactionList = Transaction.GetList(1000); 26 | 27 | var filteredTransactions = transactionList.Where(predicate).ToList(); 28 | 29 | writeAndWait($"Filtered to {filteredTransactions.Count} entities."); 30 | 31 | filteredTransactions.ForEach(Console.WriteLine); 32 | } 33 | } 34 | } 35 | -------------------------------------------------------------------------------- /ExpressionGenerator/Transaction.cs: -------------------------------------------------------------------------------- 1 | using System; 2 | using System.Collections.Generic; 3 | 4 | namespace ExpressionGenerator 5 | { 6 | public class Transaction 7 | { 8 | public int Id { get; set; } 9 | public string Category { get; set; } 10 | public string TransactionType { get; set; } 11 | public string PaymentMode { get; set; } 12 | public decimal Amount { get; set; } 13 | 14 | public static string GetOne(Random random, string[] list) 15 | => list[(int)Math.Floor(random.NextDouble() * list.Length)]; 16 | 17 | public static string[] Categories = new[] 18 | { 19 | "Clothing", 20 | "Kitchen", 21 | "Electronics", 22 | "Landscaping", 23 | "Home and Garden" 24 | }; 25 | 26 | public static string[] TransactionTypes = new[] 27 | { 28 | "payment", 29 | "income" 30 | }; 31 | 32 | public static string[] PaymentModes = new[] 33 | { 34 | "Cash", 35 | "Check", 36 | "Credit" 37 | }; 38 | 39 | public static decimal Amounts(Random random) 40 | { 41 | if (random.NextDouble() < 0.5) 42 | { 43 | return 10; 44 | } 45 | return (decimal)(random.NextDouble() * 1000); 46 | } 47 | 48 | public static List GetList(int count) 49 | { 50 | var random = new Random(); 51 | var id = 1; 52 | var result = new List 53 | { 54 | new Transaction 55 | { 56 | Id = id++, 57 | Amount = 10, 58 | Category = "Clothing", 59 | PaymentMode = "Cash", 60 | TransactionType = "income" 61 | } 62 | }; 63 | while (--count > 0) 64 | { 65 | var newTransaction = new Transaction 66 | { 67 | Id = id++, 68 | Amount = Amounts(random), 69 | Category = GetOne(random, Categories), 70 | PaymentMode = GetOne(random, PaymentModes), 71 | TransactionType = GetOne(random, TransactionTypes) 72 | }; 73 | result.Add(newTransaction); 74 | } 75 | return result; 76 | } 77 | 78 | public override string ToString() 79 | { 80 | var amount = Amount.ToString("c"); 81 | return $"Id:{Id} Category:{Category} Mode:{PaymentMode} Type:{TransactionType} Amount:{amount}"; 82 | } 83 | } 84 | } 85 | -------------------------------------------------------------------------------- /ExpressionGenerator/rules.json: -------------------------------------------------------------------------------- 1 | { 2 | "condition": "and", 3 | "rules": [ 4 | { 5 | "label": "Category", 6 | "field": "Category", 7 | "operator": "in", 8 | "type": "string", 9 | "value": [ 10 | "Clothing" 11 | ] 12 | }, 13 | { 14 | "condition": "or", 15 | "rules": [ 16 | { 17 | "label": "TransactionType", 18 | "field": "TransactionType", 19 | "operator": "equal", 20 | "type": "boolean", 21 | "value": "income" 22 | }, 23 | { 24 | "label": "PaymentMode", 25 | "field": "PaymentMode", 26 | "operator": "equal", 27 | "type": "string", 28 | "value": "Cash" 29 | } 30 | ] 31 | }, 32 | { 33 | "label": "Amount", 34 | "field": "Amount", 35 | "operator": "equal", 36 | "type": "number", 37 | "value": 10 38 | } 39 | ] 40 | } -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | MIT License 2 | 3 | Copyright (c) 2020 Jeremy Likness 4 | 5 | Permission is hereby granted, free of charge, to any person obtaining a copy 6 | of this software and associated documentation files (the "Software"), to deal 7 | in the Software without restriction, including without limitation the rights 8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 9 | copies of the Software, and to permit persons to whom the Software is 10 | furnished to do so, subject to the following conditions: 11 | 12 | The above copyright notice and this permission notice shall be included in all 13 | copies or substantial portions of the Software. 14 | 15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 21 | SOFTWARE. 22 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # ExpressionGenerator 2 | 3 | This example parses a JSON file to dynamically build a LINQ predicate that can be used to filter objects. 4 | 5 | To get started, simply clone and run. Make sure one of the `.json` source files is in your current directory (this is done automatically from Visual Studio). Each project has its own copy. 6 | 7 | The `ExpressionGenerator` project can be set as startup for LINQ to Objects. 8 | 9 | The `DatabaseTest` will apply the expressions to a locally created SQLite database. 10 | 11 | For a full explanation and walk through, read [Dynamically Build LINQ Expressions](https://blog.jeremylikness.com/blog/dynamically-build-linq-expressions/). 12 | 13 | --------------------------------------------------------------------------------