Various refactorings to support ItemFilterPreview

Filtration.Common/Utilities/LineReader.cs

@@ -0,0 +1,97 @@
+// Taken from JonSkeet's StackOverflow answer here: http://stackoverflow.com/questions/286533/filestream-streamreader-problem-in-c-sharp/286598#286598
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+namespace Filtration.Common.Utilities
+{
+
+    public sealed class LineReader : IEnumerable<string>
+    {
+        /// <summary>
+        /// Means of creating a TextReader to read from.
+        /// </summary>
+        private readonly Func<TextReader> _dataSource;
+
+        /// <summary>
+        /// Creates a LineReader from a stream source. The delegate is only
+        /// called when the enumerator is fetched. UTF-8 is used to decode
+        /// the stream into text.
+        /// </summary>
+        /// <param name="streamSource">Data source</param>
+        public LineReader(Func<Stream> streamSource)
+            : this(streamSource, Encoding.UTF8)
+        {
+        }
+
+        /// <summary>
+        /// Creates a LineReader from a stream source. The delegate is only
+        /// called when the enumerator is fetched.
+        /// </summary>
+        /// <param name="streamSource">Data source</param>
+        /// <param name="encoding">Encoding to use to decode the stream
+        /// into text</param>
+        public LineReader(Func<Stream> streamSource, Encoding encoding)
+            : this(() => new StreamReader(streamSource(), encoding))
+        {
+        }
+
+        /// <summary>
+        /// Creates a LineReader from a filename. The file is only opened
+        /// (or even checked for existence) when the enumerator is fetched.
+        /// UTF8 is used to decode the file into text.
+        /// </summary>
+        /// <param name="filename">File to read from</param>
+        public LineReader(string filename)
+            : this(filename, Encoding.UTF8)
+        {
+        }
+
+        /// <summary>
+        /// Creates a LineReader from a filename. The file is only opened
+        /// (or even checked for existence) when the enumerator is fetched.
+        /// </summary>
+        /// <param name="filename">File to read from</param>
+        /// <param name="encoding">Encoding to use to decode the file
+        /// into text</param>
+        public LineReader(string filename, Encoding encoding)
+            : this(() => new StreamReader(filename, encoding))
+        {
+        }
+
+        /// <summary>
+        /// Creates a LineReader from a TextReader source. The delegate
+        /// is only called when the enumerator is fetched
+        /// </summary>
+        /// <param name="dataSource">Data source</param>
+        public LineReader(Func<TextReader> dataSource)
+        {
+            _dataSource = dataSource;
+        }
+
+        /// <summary>
+        /// Enumerates the data source line by line.
+        /// </summary>
+        public IEnumerator<string> GetEnumerator()
+        {
+            using (TextReader reader = _dataSource())
+            {
+                string line;
+                while ((line = reader.ReadLine()) != null)
+                {
+                    yield return line;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Enumerates the data source line by line.
+        /// </summary>
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return GetEnumerator();
+        }
+    }
+}