add csharp examples (#10)

01_introduction_to_algorithms/csharp/01_binary_search/.gitignore

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+**/bin/*
+**/obj/*

01_introduction_to_algorithms/csharp/01_binary_search/.vscode/launch.json

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+{
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": ".NET Core Launch (console)",
+            "type": "coreclr",
+            "request": "launch",
+            "preLaunchTask": "build",
+            "program": "${workspaceRoot}/bin/Debug/netcoreapp1.0/01_binary_search.dll",
+            "args": [],
+            "cwd": "${workspaceRoot}",
+            "externalConsole": false,
+            "stopAtEntry": false,
+            "internalConsoleOptions": "openOnSessionStart"
+        },
+        {
+            "name": ".NET Core Attach",
+            "type": "coreclr",
+            "request": "attach",
+            "processId": "${command.pickProcess}"
+        }
+    ]
+}

01_introduction_to_algorithms/csharp/01_binary_search/.vscode/tasks.json

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+{
+    "version": "0.1.0",
+    "command": "dotnet",
+    "isShellCommand": true,
+    "args": [],
+    "tasks": [
+        {
+            "taskName": "build",
+            "args": [
+                "${workspaceRoot}/project.json"
+            ],
+            "isBuildCommand": true,
+            "problemMatcher": "$msCompile"
+        }
+    ]
+}

01_introduction_to_algorithms/csharp/01_binary_search/Program.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace ConsoleApplication
+{
+    public class Program
+    {
+        public static void Main(string[] args)
+        {
+            var myList = new List<int> { 1, 3, 5, 7, 9 };
+            Console.WriteLine(BinarySearch(myList, 3)); // => 1
+            Console.WriteLine(BinarySearch(myList, -1)); // => null gets printed as an empty string
+        }
+
+        private static int? BinarySearch(IList<int> list, int item)
+        {
+            var low = 0;
+            var high = list.Count() - 1;
+
+            while (low <= high)
+            {
+                var mid = (low + high) / 2;
+                var guess = list[mid];
+                if (guess == item) return mid;
+                if (guess > item)
+                {
+                    high = mid - 1;
+                }
+                else
+                {
+                    low = mid + 1;
+                }
+            }
+
+            return null;
+        }
+    }
+}

01_introduction_to_algorithms/csharp/01_binary_search/project.json

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+{
+  "version": "1.0.0-*",
+  "buildOptions": {
+    "debugType": "portable",
+    "emitEntryPoint": true
+  },
+  "dependencies": {},
+  "frameworks": {
+    "netcoreapp1.0": {
+      "dependencies": {
+        "Microsoft.NETCore.App": {
+          "type": "platform",
+          "version": "1.0.1"
+        }
+      },
+      "imports": "dnxcore50"
+    }
+  }
+}