Examples of errors detected by the V3139 diagnostic

V3139. Two or more case-branches perform the same actions.

.NET Core Libraries (CoreFX)

V3139 Two or more case-branches perform the same actions. WMIGenerator.cs 5220

private static string
  ConvertToNumericValueAndAddToArray(....)
{
  string retFunctionName = string.Empty;
  enumType = string.Empty;

  switch(cimType)
  {
    case CimType.UInt8:
    case CimType.SInt8:
    case CimType.SInt16:
    case CimType.UInt16:
    case CimType.SInt32:
      arrayToAdd.Add(System.Convert.ToInt32(
                       numericValue,
                       (IFormatProvider)CultureInfo.InvariantCulture
                                                   .GetFormat(typeof(int))));
      retFunctionName = "ToInt32";
      enumType = "System.Int32";
      break;

    case CimType.UInt32:
      arrayToAdd.Add(System.Convert.ToInt32(
                       numericValue,
                       (IFormatProvider)CultureInfo.InvariantCulture
                                                   .GetFormat(typeof(int))));
      retFunctionName = "ToInt32";
      enumType = "System.Int32";
      break;
    }
    return retFunctionName;
}

.NET Core Libraries (CoreFX)

V3139 Two or more case-branches perform the same actions. ColorTranslator.cs 302

switch (c.ToKnownColor())
{
  ....
  case KnownColor.Control:
    colorString = "buttonface";
    break;
  case KnownColor.ControlLight:
    colorString = "buttonface";
    break;
  ....
}

Roslyn Analyzers

V3139 Two or more case-branches perform the same actions. CodeMetricsAnalyzer.cs 251

static bool isApplicableByDefault(string ruleId, SymbolKind symbolKind)
{
  switch (ruleId)
  {
     ....
     case CA1505RuleId:
       switch (symbolKind)
       {
          case SymbolKind.NamedType:
          case SymbolKind.Method:
          case SymbolKind.Field:
          case SymbolKind.Property:
          case SymbolKind.Event:
            return true;
          default:
            return false;
       }
     case CA1506RuleId:
       switch (symbolKind)
       {
          case SymbolKind.NamedType:
          case SymbolKind.Method:
          case SymbolKind.Field:
          case SymbolKind.Property:
          case SymbolKind.Event:
            return true;
          default:
            return false;
       }
     default:
       throw new NotImplementedException();
  }
}