ASP2XML: Convert Classic ASP Data to XML Quickly

Troubleshooting ASP2XML: Common Issues and Fixes

Overview

This guide covers frequent problems when using ASP2XML (converting Classic ASP output to XML) and provides targeted fixes and examples to get your XML generation reliable and well-formed.

1. Problem: Malformed XML (invalid characters or structure)

• Cause: Unescaped special characters (&, <, >, “, ‘) or unexpected HTML fragments in output.
• Fix:
  1. Always escape data before writing to XML. Use helper functions:

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     Function XmlEscape(s) If IsNull(s) Then XmlEscape = “”   s = Replace(s, “&”, “&”)   s = Replace(s, “<”, “<”)   s = Replace(s, “>”, “>”)   s = Replace(s, “”“”, “”“)   s = Replace(s, “’”, “‘”)   XmlEscape = s End Function 

  2. Strip or encode HTML if content includes markup (Server.HTMLEncode for visible HTML entities).
  3. Validate structure: ensure one root element and properly nested tags.

2. Problem: Incorrect Content-Type or encoding

• Cause: Browser or client misinterprets XML due to wrong headers or character encoding mismatch.
• Fix:
  1. Send correct headers before any output:

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     Response.ContentType = “text/xml” Response.Charset = “utf-8” 

  2. If emitting XML declaration, ensure encoding matches:

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     Response.Write “<?xml version=”“1.0”” encoding=““utf-8”“?>” 

  3. For non-UTF-8 data (legacy codepages), convert strings to UTF-8 or set matching charset.

3. Problem: BOM or whitespace before XML declaration

• Cause: Any output (even whitespace) prior to XML declaration breaks XML parsers.
• Fix:
  1. Turn off buffering only if you handle output order — otherwise use buffering:

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     Response.Buffer = True 

  2. Ensure no include files, ASP/VBScript code, or editors add BOM/leading whitespace. Save files without BOM (UTF-8 without BOM).
  3. Write the XML declaration as the very first bytes:

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     Response.Clear Response.Write “<?xml version=”“1.0”” encoding=““utf-8”“?>” & vbCrLf 

4. Problem: Improper handling of recordset data (NULLs, datatypes)

• Cause: NULL values or binary data breaking XML structure; date/number formatting issues.
• Fix:
  1. Normalize values when reading recordsets:

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     Function SafeValue(v)   If IsNull(v) Then SafeValue = “”   ElseIf IsDate(v) Then SafeValue = Year(v) & “-” & Right(“0” & Month(v),2) & “-” & Right(“0” & Day(v),2)   Else SafeValue = XmlEscape(CStr(v))   End If End Function 

  2. Convert binary/blobs to base64 if embedding in XML.
  3. Explicitly format numbers using CStr or FormatNumber to avoid locale issues.

5. Problem: Large datasets cause slow response or memory issues

• Cause: Building large XML strings in memory or unbuffered streaming.
• Fix:
  1. Stream output row-by-row rather than concatenating large strings:

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     Response.Buffer = False Response.Write “<?xml version=”“1.0”” encoding=““utf-8”“?>” Do While Not rs.EOF   Response.Write “”   Response.Write “” & XmlEscape(rs(“id”)) & “”   …   Response.Write “”   rs.MoveNext Loop Response.Write “” 

  2. Use server-side pagination and limit resultset size.
  3. If buffering, ensure Response.Buffer = True only for moderate-sized outputs.

6. Problem: Namespaces and special XML features not supported

• Cause: Simple string-generation approach ignores namespaces,