System.Globalization.CultureNotFoundException – Culture is not supported

The System.Globalization.CultureNotFoundException with the message “Culture is not supported” occurs in C# when you attempt to use a culture that is not recognized or supported by the .NET runtime. This typically happens when you provide an invalid culture name or identifier, or when the required culture data is not installed on the system.

Common Causes and Solutions

1. Invalid Culture Name or Identifier:
   If you provide an invalid culture name or identifier, this exception will occur.

   var culture = new CultureInfo("xx-XX"); // CultureNotFoundException – Invalid culture name

Fix: Use a valid culture name or identifier.

   var culture = new CultureInfo("en-US"); // Valid culture name

2. Custom Cultures:
   If you attempt to use a custom culture that is not registered or supported, this exception can occur. Fix: Ensure the custom culture is registered or use a built-in culture.

   var culture = new CultureInfo("en-CA"); // Use a built-in culture

3. Missing Culture Data:
   If the required culture data is not installed on the system, this exception can occur. Fix: Install the required culture data or use a fallback culture.

   var culture = CultureInfo.GetCultureInfo("fr-FR"); // Fallback to a supported culture

4. Neutral Cultures:
   If you attempt to use a neutral culture (e.g., “en” instead of “en-US”) in a context that requires a specific culture, this exception can occur. Fix: Use a specific culture instead of a neutral culture.

   var culture = new CultureInfo("en-US"); // Specific culture

5. Case Sensitivity:
   Culture names are case-insensitive, but if you provide an invalid format, this exception can occur. Fix: Use the correct format for culture names.

   var culture = new CultureInfo("en-us"); // Correct format

6. Using CultureInfo.CreateSpecificCulture:
   If you use CultureInfo.CreateSpecificCulture with an invalid culture name, this exception can occur. Fix: Ensure the culture name is valid.

   var culture = CultureInfo.CreateSpecificCulture("en-US"); // Valid culture name

7. Fallback to Invariant Culture:
   If the specified culture is not supported, you can fallback to the invariant culture. Fix: Use the invariant culture as a fallback.

   var culture = CultureInfo.GetCultureInfo("xx-XX") ?? CultureInfo.InvariantCulture; // Fallback to invariant culture

8. Checking Culture Support:
   You can check if a culture is supported before using it. Fix: Use CultureInfo.GetCultures to check for supported cultures.

   var supportedCultures = CultureInfo.GetCultures(CultureTypes.AllCultures);
   var culture = supportedCultures.FirstOrDefault(c => c.Name == "en-US") ?? CultureInfo.InvariantCulture;