C# Add line of code metric query

Author: tamasvajk

csharp/ql/src/Metrics/Summaries/LinesOfCode.ql

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+/**
+ * @id cs/summary/lines-of-code
+ * @name Total lines of code in the database
+ * @description The total number of lines of code across all files. This is a useful metric of the size of a database. For all files that were seen during the build, this query counts the lines of code, excluding whitespace or comments.
+ * @kind metric
+ * @tags summary
+ */
+
+import csharp
+
+select sum(File f | f.fromSource() | f.getNumberOfLinesOfCode())

csharp/ql/test/query-tests/Metrics/Summaries/LinesOfCode.expected

@@ -0,0 +1 @@
+| 4 |

csharp/ql/test/query-tests/Metrics/Summaries/LinesOfCode.qlref

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+Metrics/Summaries/LinesOfCode.ql

csharp/ql/test/query-tests/Metrics/Summaries/file1.cs

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+
+class C1
+{
+    /*
+      int M()
+      {
+        return 0;
+      }
+    */
+
+    // int M() => 0;
+
+    int M() => 0; // Comment
+}