Simplify logic in EscapeString.

Author: bgrainger

src/MySqlConnector/MySqlClient/MySqlHelper.cs

@@ -24,15 +24,14 @@ public static string EscapeString(string value)
 				{
 					if (sb == null)
 						sb = new StringBuilder();
-					if (i > last - 1)
-						sb.Append(value, last + 1, i - last - 1);
+					sb.Append(value, last + 1, i - (last + 1));
 					sb.Append('\\');
 					sb.Append(value[i]);
 					last = i;
 				}
 			}
-			if (sb != null && last < value.Length - 1)
-				sb.Append(value, last + 1, value.Length - last - 1);
+			if (sb != null)
+				sb.Append(value, last + 1, value.Length - (last + 1));
 
 			return sb?.ToString() ?? value;
 		}

tests/MySqlConnector.Tests/MySqlHelperTests.cs

@@ -9,11 +9,13 @@ public class MySqlHelperTests
 		[InlineData("", "")]
 		[InlineData("test", "test")]
 		[InlineData("\"", "\\\"")]
-		[InlineData("'", "\\'")]
-		[InlineData("\\", "\\\\")]
+		[InlineData(@"'", @"\'")]
+		[InlineData(@"\", @"\\")]
+		[InlineData(@"''", @"\'\'")]
 		[InlineData(@"'begin", @"\'begin")]
 		[InlineData(@"end'", @"end\'")]
 		[InlineData(@"mid'dle", @"mid\'dle")]
+		[InlineData(@"doub''led", @"doub\'\'led")]
 		[InlineData(@"'a'b'", @"\'a\'b\'")]
 		public void EscapeString(string input, string expected)
 		{