Added "ExportAsMemoryStream", less allocations in file export

CsvExport/CsvExport.cs

@@ -229,43 +229,52 @@ public string Export()
 		/// </summary>
 		public void ExportToFile(string path, Encoding encoding = null)
 		{
-			File.WriteAllBytes(path, ExportToBytes(encoding ?? _defaultEncoding));
+			using var fs = new FileStream(path, FileMode.Create, FileAccess.Write);
+			using var ms = ExportAsMemoryStream(encoding);
+			ms.WriteTo(fs);
 		}
 
 		/// <summary>
 		/// Exports as raw bytes.
 		/// </summary>
 		public byte[] ExportToBytes(Encoding encoding = null)
 		{
-			using (MemoryStream ms = new MemoryStream())
-			{
-				encoding = encoding ?? _defaultEncoding;
-				var preamble = encoding.GetPreamble();
-				ms.Write(preamble, 0, preamble.Length);
+			using var ms = ExportAsMemoryStream(encoding);
+			return ms.ToArray();
+		}
+
+		public MemoryStream ExportAsMemoryStream(Encoding encoding = null)
+		{
+			MemoryStream ms = new MemoryStream();
 
+			encoding = encoding ?? _defaultEncoding;
+			var preamble = encoding.GetPreamble();
+			ms.Write(preamble, 0, preamble.Length);
 
-				using (var sw = new StreamWriter(ms, encoding))
-				{
-					if (_includeColumnSeparatorDefinitionPreamble)
-						sw.Write("sep=" + _columnSeparator + "\r\n");
+			using (var sw = new StreamWriter(ms, encoding, 1024, leaveOpen: true))
+			{
+				if (_includeColumnSeparatorDefinitionPreamble)
+					sw.Write("sep=" + _columnSeparator + "\r\n");
 
-					foreach (var line in ExportToLines())
+				foreach (var line in ExportToLines())
+				{
+					int i = 0;
+					foreach (var value in line)
 					{
-						int i = 0;
-						foreach (var value in line)
-						{
-							sw.Write(value);
-
-							if (++i != _fields.Count)
-								sw.Write(_columnSeparator);
-						}
-						sw.Write("\r\n");
-					}
+						sw.Write(value);
 
-					sw.Flush(); //otherwise we're risking empty stream
+						if (++i != _fields.Count)
+							sw.Write(_columnSeparator);
+					}
+					sw.Write("\r\n");
 				}
-				return ms.ToArray();
+
+				sw.Flush(); //otherwise we're risking empty stream
 			}
+
+			ms.Position = 0;
+
+			return ms;
 		}
 	}
 }

UnitTests/UnitTests.cs

@@ -81,6 +81,29 @@ public void TestGeneric()
 
 			Assert.IsTrue(csv.Trim() == "sep=,\r\nId,Name\r\n123,Ffff\r\n321,ddd", csv);
 		}
+
+		[TestMethod]
+		public void WriteToFile()
+		{
+			var myExport = new CsvExport();
+			myExport.AddRow();
+			myExport["Region"] = "Los Angeles, USA";
+			myExport["Sales"] = 100000;
+			myExport["Date Opened"] = new DateTime(2003, 12, 31);
+
+			myExport.AddRow();
+			myExport["Region"] = "Canberra \"in\" Australia";
+			myExport["Sales"] = 50000;
+			myExport["Date Opened"] = new DateTime(2005, 1, 1, 9, 30, 0);
+
+			var filePath = Path.GetTempFileName();
+			myExport.ExportToFile(filePath);
+
+			Assert.IsTrue(File.Exists(filePath));
+			Assert.IsTrue(File.ReadAllText(filePath).Trim() == "sep=,\r\nRegion,Sales,Date Opened\r\n\"Los Angeles, USA\",100000,2003-12-31\r\n\"Canberra \"\"in\"\" Australia\",50000,2005-01-01 09:30:00", File.ReadAllText(filePath));
+
+			File.Delete(filePath);
+		}
 	}
 
 	public class MyClass