Working on linq queries

.vscode/launch.json

@@ -0,0 +1,27 @@
+{
+    "version": "0.2.0",
+    "configurations": [
+        {
+            // Use IntelliSense to find out which attributes exist for C# debugging
+            // Use hover for the description of the existing attributes
+            // For further information visit https://github.com/OmniSharp/omnisharp-vscode/blob/master/debugger-launchjson.md
+            "name": ".NET Core Launch (console)",
+            "type": "coreclr",
+            "request": "launch",
+            "preLaunchTask": "build",
+            // If you have changed target frameworks, make sure to update the program path.
+            "program": "${workspaceFolder}/Introduction/bin/Debug/netcoreapp3.1/Introduction.dll",
+            "args": [],
+            "cwd": "${workspaceFolder}/Introduction",
+            // For more information about the 'console' field, see https://aka.ms/VSCode-CS-LaunchJson-Console
+            "console": "internalConsole",
+            "stopAtEntry": false
+        },
+        {
+            "name": ".NET Core Attach",
+            "type": "coreclr",
+            "request": "attach",
+            "processId": "${command:pickProcess}"
+        }
+    ]
+}

.vscode/tasks.json

@@ -0,0 +1,42 @@
+{
+    "version": "2.0.0",
+    "tasks": [
+        {
+            "label": "build",
+            "command": "dotnet",
+            "type": "process",
+            "args": [
+                "build",
+                "${workspaceFolder}/Introduction/Introduction.csproj",
+                "/property:GenerateFullPaths=true",
+                "/consoleloggerparameters:NoSummary"
+            ],
+            "problemMatcher": "$msCompile"
+        },
+        {
+            "label": "publish",
+            "command": "dotnet",
+            "type": "process",
+            "args": [
+                "publish",
+                "${workspaceFolder}/Introduction/Introduction.csproj",
+                "/property:GenerateFullPaths=true",
+                "/consoleloggerparameters:NoSummary"
+            ],
+            "problemMatcher": "$msCompile"
+        },
+        {
+            "label": "watch",
+            "command": "dotnet",
+            "type": "process",
+            "args": [
+                "watch",
+                "run",
+                "${workspaceFolder}/Introduction/Introduction.csproj",
+                "/property:GenerateFullPaths=true",
+                "/consoleloggerparameters:NoSummary"
+            ],
+            "problemMatcher": "$msCompile"
+        }
+    ]
+}

Queries/Movie.cs

@@ -0,0 +1,22 @@
+using System;
+
+namespace Queries
+{
+    public class Movie
+    {
+        public string Title { get; set; }
+        public float Rating { get; set; }
+        private int _year;
+        public int Year {
+            get
+            {
+                Console.WriteLine($"Returning {_year} for {Title}");
+                return _year;
+            }
+            set
+            {
+                _year = value;
+            }
+        }
+    }
+}

Queries/MyLinq.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using System.Dynamic;
+using System.Reflection;
+
+namespace Queries
+{
+    public static class MyLinq
+    {
+        public static IEnumerable<T> Filter<T>(this IEnumerable<T> source, 
+            Func<T, bool> predicate)
+        {
+            // define a customized filter extension for LINQ
+            // demonstrate how to create a customized LINQ filter
+            var result = new List<T>();
+
+            foreach (var item in source)
+            {
+                if (predicate(item))
+                {
+                    yield return item;
+                }
+            }
+        }
+    }
+}

Queries/Program.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Queries
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            var movies = new List<Movie>
+            {
+                new Movie {Title = "The Dark Knight", Rating = 8.9f, Year = 2008},
+                new Movie {Title = "The King's Speech", Rating = 8.0f, Year = 2010},
+                new Movie {Title = "Casablanca", Rating = 8.5f, Year = 1942},
+                new Movie {Title = "Star Wars V", Rating = 8.5f, Year = 1980}
+            };
+
+            // filter operator from LINQ
+            Console.WriteLine();
+            Console.WriteLine("Filter operator from LINQ");
+            var query = movies.Where(m => m.Year > 2000);
+            foreach (var movie in query)
+            {
+                Console.WriteLine(movie.Title);
+            }
+            
+            // filter operator using customized Filter extension
+            Console.WriteLine();
+            Console.WriteLine("Customerized Filter operator");
+            var query2 = movies.Filter(m => m.Year > 2000);
+            foreach (var movie in query2)
+            {
+                Console.WriteLine(movie.Title);
+            }
+        }
+    }
+}

Queries/Queries.csproj

@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <OutputType>Exe</OutputType>
+        <TargetFramework>netcoreapp3.1</TargetFramework>
+    </PropertyGroup>
+
+</Project>

linq-fundamentals.sln

@@ -7,6 +7,10 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Introduction", "Introductio
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Features", "Features\Features.csproj", "{94C9EE4C-0609-464B-9BFF-BA3EED2A7263}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Queries", "Queries\Queries.csproj", "{FB21B6B5-70C3-444E-A1D1-2CCD3F575DD9}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "yield_test", "yield_test\yield_test.csproj", "{790E4D64-D90A-4289-9F5D-35B6A2BDBE5B}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -44,5 +48,29 @@ Global
 		{94C9EE4C-0609-464B-9BFF-BA3EED2A7263}.Release|x64.Build.0 = Release|Any CPU
 		{94C9EE4C-0609-464B-9BFF-BA3EED2A7263}.Release|x86.ActiveCfg = Release|Any CPU
 		{94C9EE4C-0609-464B-9BFF-BA3EED2A7263}.Release|x86.Build.0 = Release|Any CPU
+		{FB21B6B5-70C3-444E-A1D1-2CCD3F575DD9}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{FB21B6B5-70C3-444E-A1D1-2CCD3F575DD9}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{FB21B6B5-70C3-444E-A1D1-2CCD3F575DD9}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{FB21B6B5-70C3-444E-A1D1-2CCD3F575DD9}.Debug|x64.Build.0 = Debug|Any CPU
+		{FB21B6B5-70C3-444E-A1D1-2CCD3F575DD9}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{FB21B6B5-70C3-444E-A1D1-2CCD3F575DD9}.Debug|x86.Build.0 = Debug|Any CPU
+		{FB21B6B5-70C3-444E-A1D1-2CCD3F575DD9}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{FB21B6B5-70C3-444E-A1D1-2CCD3F575DD9}.Release|Any CPU.Build.0 = Release|Any CPU
+		{FB21B6B5-70C3-444E-A1D1-2CCD3F575DD9}.Release|x64.ActiveCfg = Release|Any CPU
+		{FB21B6B5-70C3-444E-A1D1-2CCD3F575DD9}.Release|x64.Build.0 = Release|Any CPU
+		{FB21B6B5-70C3-444E-A1D1-2CCD3F575DD9}.Release|x86.ActiveCfg = Release|Any CPU
+		{FB21B6B5-70C3-444E-A1D1-2CCD3F575DD9}.Release|x86.Build.0 = Release|Any CPU
+		{790E4D64-D90A-4289-9F5D-35B6A2BDBE5B}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{790E4D64-D90A-4289-9F5D-35B6A2BDBE5B}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{790E4D64-D90A-4289-9F5D-35B6A2BDBE5B}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{790E4D64-D90A-4289-9F5D-35B6A2BDBE5B}.Debug|x64.Build.0 = Debug|Any CPU
+		{790E4D64-D90A-4289-9F5D-35B6A2BDBE5B}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{790E4D64-D90A-4289-9F5D-35B6A2BDBE5B}.Debug|x86.Build.0 = Debug|Any CPU
+		{790E4D64-D90A-4289-9F5D-35B6A2BDBE5B}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{790E4D64-D90A-4289-9F5D-35B6A2BDBE5B}.Release|Any CPU.Build.0 = Release|Any CPU
+		{790E4D64-D90A-4289-9F5D-35B6A2BDBE5B}.Release|x64.ActiveCfg = Release|Any CPU
+		{790E4D64-D90A-4289-9F5D-35B6A2BDBE5B}.Release|x64.Build.0 = Release|Any CPU
+		{790E4D64-D90A-4289-9F5D-35B6A2BDBE5B}.Release|x86.ActiveCfg = Release|Any CPU
+		{790E4D64-D90A-4289-9F5D-35B6A2BDBE5B}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 EndGlobal

yield_test/Program.cs

@@ -0,0 +1,23 @@
+using System;
+using System.Collections;
+
+namespace yield_test
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            foreach (var number in GetNumbers())
+            {
+                Console.WriteLine(number);
+            }
+        }
+
+        static IEnumerable GetNumbers()
+        {
+            yield return 1;
+            yield return 2;
+            yield return 3;
+        }
+    }
+}

yield_test/yield_test.csproj

@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <OutputType>Exe</OutputType>
+        <TargetFramework>netcoreapp3.1</TargetFramework>
+    </PropertyGroup>
+
+</Project>