Update snippets per issue. (#37793)

* Update snippets per issue.

* Add project file.

* Troubleshoot snippet build error.

* Troubleshoot snippet error.

Author: TimShererWithAquent

samples/snippets/csharp/VS_Snippets_CLR_System/system.IO.StreamReader/CS/compose.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <StartupObject>CompBuf</StartupObject>
+  </PropertyGroup>
+
+</Project>

samples/snippets/csharp/VS_Snippets_CLR_System/system.IO.StreamReader/CS/source2.cs

@@ -13,11 +13,8 @@ public static void Main()
             Console.WriteLine($"{FILE_NAME} does not exist!");
             return;
         }
-        FileStream fsIn = new FileStream(FILE_NAME, FileMode.Open,
-            FileAccess.Read, FileShare.Read);
-        // Create an instance of StreamReader that can read
-        // characters from the FileStream.
-        using (StreamReader sr = new StreamReader(fsIn))
+        // Create an instance of StreamReader characters from the file.
+        using (StreamReader sr = new StreamReader(FILE_NAME))
         {
             string input;
             // While not at the end of the file, read lines from the file.

samples/snippets/csharp/VS_Snippets_CLR_System/system.IO.StreamReader/CS/source3.cs

@@ -13,18 +13,19 @@ public static void Main()
             Console.WriteLine($"{FILE_NAME} does not exist.");
             return;
         }
-        FileStream f = new FileStream(FILE_NAME, FileMode.Open,
-            FileAccess.Read, FileShare.Read);
-        // Create an instance of BinaryReader that can
-        // read bytes from the FileStream.
-        using (BinaryReader br = new BinaryReader(f))
+        using (FileStream f = new FileStream(FILE_NAME, FileMode.Open, FileAccess.Read, FileShare.Read))
         {
-            byte input;
-            // While not at the end of the file, read lines from the file.
-            while (br.PeekChar() > -1 )
+            // Create an instance of BinaryReader that can
+            // read bytes from the FileStream.
+            using (BinaryReader br = new BinaryReader(f))
             {
-                input = br.ReadByte();
-                Console.WriteLine(input);
+                byte input;
+                // While not at the end of the file, read lines from the file.
+                while (br.PeekChar() > -1)
+                {
+                    input = br.ReadByte();
+                    Console.WriteLine(input);
+                }
             }
         }
     }