Table of Contents

Avoid Invalid Characters in Descriptions

  • 2026-01-09
  • Morten Lønskov

Overview

This best practice rule identifies objects whose descriptions contain invalid control characters (non-printable characters excluding standard whitespace). These characters can cause display problems, metadata corruption, and deployment failures.

  • Category: Error Prevention
  • Severity: High (3)

Applies To

  • Tables
  • Measures
  • Hierarchies
  • Levels
  • Perspectives
  • Partitions
  • Data Columns
  • Calculated Columns
  • Calculated Table Columns
  • KPIs
  • Model Roles
  • Calculation Groups
  • Calculation Items

Why This Matters

Control characters in descriptions cause various issues:

  • Display corruption: Tooltips and documentation panels may show garbled text
  • Metadata problems: TMSL/XMLA export may produce invalid XML
  • Deployment failures: Power BI Service or Analysis Services may reject the model
  • Documentation issues: Generated documentation may break formatting
  • Encoding errors: Cross-platform synchronization problems
  • User confusion: Invisible characters create confusing or corrupted descriptions

Standard whitespace (spaces, newlines, tabs) is acceptable, but non-printable control characters should be removed.

When This Rule Triggers

The rule triggers when an object's description contains control characters that are not standard whitespace:

Description.ToCharArray().Any(char.IsControl(it) and !char.IsWhiteSpace(it))

This detects problematic characters while allowing legitimate whitespace formatting.

How to Fix

Automatic Fix

This rule includes an automatic fix that replaces invalid characters with spaces:

Description = string.Concat(
    it.Description.ToCharArray().Select(
        c => (char.IsControl(c) && !char.IsWhiteSpace(c)) ? ' ' : c
    )
)

To apply:

  1. In the Best Practice Analyzer select flagged objects
  2. Click Apply Fix

Manual Fix

  1. In TOM Explorer, select the object
  2. In Properties pane, locate the Description field
  3. Edit the description to remove invalid characters
  4. Save changes

Common Causes

Cause 1: Copy/Paste from Rich Text

Copying descriptions from Word documents, web pages, or emails can introduce hidden formatting characters.

Cause 2: Automated Documentation Generation

Scripts generating descriptions may include control characters from source systems.

Cause 3: Data Import from External Sources

Importing metadata that contains encoding artifacts or control codes.

Example

Before Fix

Measure: [Total Revenue]
Description: "Calculates\x00total\x0Brevenue"  (contains NULL and vertical tab)

Tooltip displays: "Calculatesâ–ˇtotalâ–ˇrevenue" (with visible corruption)

After Fix

Measure: [Total Revenue]
Description: "Calculates total revenue"  (control characters replaced with spaces)

Tooltip displays correctly: "Calculates total revenue"

Compatibility Level

This rule applies to models with compatibility level 1200 and higher.