Serialize numbers with invariant culture.

RestSharp/Serializers/XmlSerializer.cs

@@ -179,10 +179,52 @@ public class XmlSerializer : ISerializer
 			{
 				output = ((bool)obj).ToString(CultureInfo.InvariantCulture).ToLower();
 			}
+			if (IsNumeric(obj))
+			{
+				return SerializeNumber(obj);
+			}
 
 			return output.ToString();
 		}
 
+		static string SerializeNumber(object number)
+		{
+			if (number is long)
+				return ((long)number).ToString(CultureInfo.InvariantCulture);
+			else if (number is ulong)
+				return ((ulong)number).ToString(CultureInfo.InvariantCulture);
+			else if (number is int)
+				return ((int)number).ToString(CultureInfo.InvariantCulture);
+			else if (number is uint)
+				return ((uint)number).ToString(CultureInfo.InvariantCulture);
+			else if (number is decimal)
+				return ((decimal)number).ToString(CultureInfo.InvariantCulture);
+			else if (number is float)
+				return ((float)number).ToString(CultureInfo.InvariantCulture);
+			else
+				return (Convert.ToDouble(number, CultureInfo.InvariantCulture).ToString("r", CultureInfo.InvariantCulture));
+		}
+
+		/// <summary>
+		/// Determines if a given object is numeric in any way
+		/// (can be integer, double, null, etc).
+		/// </summary>
+		static bool IsNumeric(object value)
+		{
+			if (value is sbyte) return true;
+			if (value is byte) return true;
+			if (value is short) return true;
+			if (value is ushort) return true;
+			if (value is int) return true;
+			if (value is uint) return true;
+			if (value is long) return true;
+			if (value is ulong) return true;
+			if (value is float) return true;
+			if (value is double) return true;
+			if (value is decimal) return true;
+			return false;
+		}
+
 		/// <summary>
 		/// Name of the root element to use when serializing
 		/// </summary>