Added some useful parsing functions.

OsmToDatabase.Common/TagParsing.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using OsmSharp;
+using OsmSharp.Tags;
+
+namespace OsmToDatabase.Common
+{
+    public static class TagParsing
+    {
+        /// <summary>
+        /// Gets the value of a tag with the given key.
+        /// </summary>
+        /// <param name="node">Node that is being searched for tags.</param>
+        /// <param name="tagKey">Key of the tag that is being searched for.</param>
+        /// <returns>Value of the tag, or null if it is not found.</returns>
+        public static string? TagValueByKey(this Node node, string tagKey)
+        {
+            return node
+                .Tags.Select<Tag, Tag?>(t => t)
+                .FirstOrDefault(tag => tag is not null && tag.Value.Key == tagKey)
+                ?.Value;
+        }
+
+        public static double? TagDoubleValueByKey(this Node node, string tagKey)
+        {
+            string? tagValue = node.TagValueByKey(tagKey);
+            bool success = double.TryParse(tagValue, out double result);
+            return success ? result : null;
+        }
+    }
+}