Users/abbasc52/doc updates (#555)

* added custom type injection in docs

* updated expression parser to support null Resettings and added standalone evaluator sample

* fixed missing bracket

Author: abbasc52

docs/index.md

@@ -9,6 +9,7 @@ RulesEngine is a highly extensible library to build rule based system using C# e
 - Extending expression via custom class/type injection
 - Scoped parameters
 - Post rule execution actions
+- Standalone expression evaluator
 
 **Table Of Content**
 - [Installation](#installation)
@@ -18,11 +19,13 @@ RulesEngine is a highly extensible library to build rule based system using C# e
   - [Execute the workflow rules with input:](#execute-the-workflow-rules-with-input)
   - [Using custom names for inputs](#using-custom-names-for-inputs)
 - [C# Expression support](#c-expression-support)
+- [Extending expression via custom class/type injection](#extending-expression-via-custom-classtype-injection)
+  - [Example](#example)
 - [ScopedParams](#scopedparams)
   - [GlobalParams](#globalparams)
-    - [Example](#example)
-  - [LocalParams](#localparams)
     - [Example](#example-1)
+  - [LocalParams](#localparams)
+    - [Example](#example-2)
   - [Referencing ScopedParams in other ScopedParams](#referencing-scopedparams-in-other-scopedparams)
 - [Post rule execution actions](#post-rule-execution-actions)
   - [Inbuilt Actions](#inbuilt-actions)
@@ -32,6 +35,8 @@ RulesEngine is a highly extensible library to build rule based system using C# e
       - [Usage](#usage-1)
   - [Custom Actions](#custom-actions)
     - [Steps to use a custom Action](#steps-to-use-a-custom-action)
+- [Standalone Expression Evaluator](#standalone-expression-evaluator)
+  - [Usage](#usage-2)
 
 
 
@@ -123,6 +128,59 @@ For more details on supported expression language refer - [expression language](
 For supported linq operations refer - [sequence operators](https://dynamic-linq.net/expression-language#sequence-operators)
 
 
+## Extending expression via custom class/type injection
+Although RulesEngine supports C# expressions, you may need to perform more complex operation.
+
+RulesEngine supports injecting custom classes/types via `ReSettings` which can allow you to call properties and methods of your custom class in expressions
+
+### Example
+Create a custom static class
+```c#
+using System;
+using System.Linq;
+
+namespace RE.HelperFunctions
+{
+    public static class Utils
+    {
+        public static bool CheckContains(string check, string valList)
+        {
+            if (String.IsNullOrEmpty(check) || String.IsNullOrEmpty(valList))
+                return false;
+
+            var list = valList.Split(',').ToList();
+            return list.Contains(check);
+        }
+    }
+}
+```
+
+Add it in your ReSettings and pass in RulesEngine constructor
+
+```c#
+  var reSettings = new ReSettings{
+      CustomTypes = new Type[] { typeof(Utils) }
+  }
+
+  var rulesEngine = new RulesEngine.RulesEngine(workflowRules,reSettings);
+```
+
+With this you can call Utils class in your Rules
+
+```json
+{
+    "WorkflowName": "DiscountWithCustomInputNames",
+    "Rules": [
+      {
+        "RuleName": "GiveDiscount10",
+        "Expression": "Utils.CheckContains(input1.country, \"india,usa,canada,France\") == true"
+      }
+    ]
+}
+
+```
+
+
 ## ScopedParams
 Sometimes Rules can get very long and complex, scopedParams allow users to replace an expression in rule with an alias making it easier to maintain rule.
 
@@ -471,5 +529,29 @@ Actions can have async code as well
 }
 ```
 
+## Standalone Expression Evaluator
+If you are not looking for a full fledged RulesEngine and need only an expression evaluator. RulesEngine offers `RuleExpressionParser` which handles expression parsing and evaluation.
+
+### Usage
+```c#
+using System;
+using RulesEngine.Models;
+using RulesEngine.ExpressionBuilders;
+					
+public class Program
+{
+	public static void Main()
+	{
+		var reParser = new RuleExpressionParser(new ReSettings());
+		var result = reParser.Evaluate<string>("a+b", new RuleParameter[]{
+			new RuleParameter("a","Hello "),
+			new RuleParameter("b","World")
+		});
+		Console.WriteLine(result);
+	}
+}
+```
+This will output "Hello World"
+
+For more advanced usage, refer - https://dotnetfiddle.net/KSX8i0
 
-_For more details please check out [Rules Engine Wiki](https://github.com/microsoft/RulesEngine/wiki)._

src/RulesEngine/ExpressionBuilders/RuleExpressionParser.cs

@@ -19,9 +19,9 @@ public class RuleExpressionParser
         private readonly ReSettings _reSettings;
         private readonly IDictionary<string, MethodInfo> _methodInfo;
 
-        public RuleExpressionParser(ReSettings reSettings)
+        public RuleExpressionParser(ReSettings reSettings = null)
         {
-            _reSettings = reSettings;
+            _reSettings = reSettings ?? new ReSettings();
             _methodInfo = new Dictionary<string, MethodInfo>();
             PopulateMethodInfo();
         }

test/RulesEngine.UnitTest/TypedClassTests.cs

@@ -120,11 +120,11 @@ public async Task TypedClassInputSameNameAsTypeTest()
             var re = new RulesEngine(reSettings);
             re.AddWorkflow(workflow);
 
-            var param = new Transazione {
+            var param = new Transazione {
                 Attori = new List<Attore>{
                     new Attore{
-                        RuoloAttore = RuoloAttore.B,
-
+                        RuoloAttore = RuoloAttore.B,
+
                     },
                     new Attore {
                          RuoloAttore = RuoloAttore.C
@@ -137,9 +137,9 @@ public async Task TypedClassInputSameNameAsTypeTest()
 
             Assert.All(result, (res) => Assert.True(res.IsSuccess));
 
-        }
-
-
+        }
+
+
         [Fact]
         public async Task TypedClassBothAccessibleTestWhenCaseInsensitive()
         {
@@ -163,8 +163,8 @@ public async Task TypedClassBothAccessibleTestWhenCaseInsensitive()
                         Expression = "transazione.Attori != null",
                     },
                      new() {
-                        RuleName = "Static FieldTest",
-                        Expression = "Transazione.StaticProperty == \"Hello\""
+                        RuleName = "Static FieldTest",
+                        Expression = "Transazione.StaticProperty == \"Hello\""
                     }
                 }
             };
@@ -177,11 +177,11 @@ public async Task TypedClassBothAccessibleTestWhenCaseInsensitive()
             var re = new RulesEngine(reSettings);
             re.AddWorkflow(workflow);
 
-            var param = new Transazione {
+            var param = new Transazione {
                 Attori = new List<Attore>{
                     new Attore{
-                        RuoloAttore = RuoloAttore.B,
-
+                        RuoloAttore = RuoloAttore.B,
+
                     },
                     new Attore {
                          RuoloAttore = RuoloAttore.C