Translate a .NET app into Spanish: localising your .resx files

What changes when a .NET interface moves to Spanish

Spanish runs longer than English. In a WinForms or WPF app with fixed-width labels, Settings becomes Configuración and Sign in becomes Iniciar sesión, so buttons and grid columns sized for English will clip or overflow.

Three Spanish-specific decisions to make before translating:

• Opening punctuation. Questions and exclamations open with ¿ or ¡: Delete this file? becomes ¿Eliminar este archivo?. If your code appends the question mark itself, the opening mark has nowhere to go.
• Register. Introduce tu contraseña (informal tú, common in consumer apps in Spain) or Introduzca su contraseña (formal usted, usual in business software and much of Latin America). Mixing them across screens is immediately noticeable.
• Variant. ordenador or computadora, fichero or archivo, móvil or celular: decide whether you are targeting Spain, Mexico or a neutral Spanish.

Numbers and dates belong to the .NET culture, not to the translation: under es-ES, {0:N2} renders 1.234,56; under es-MX, 1,234.56. Never hard-code a format inside a resource value.

Composite strings, plurals and grammatical gender

String.Format placeholders are positional, so Spanish can reorder the sentence: {0} of {1} items selected becomes {0} de {1} elementos seleccionados, and {1:d} keeps its format specifier. Every {n} in the source must appear in the translation, no more and no fewer.

.resx has no plural mechanism, so most projects use one key per form, such as FilesCount_One and FilesCount_Other. CLDR gives Spanish three categories: one, many and other. One covers 1 (1 archivo), other covers 0 and everything else (0 archivos, 3 archivos), and many applies to round millions, which take de: 1 millón de archivos. If your counters can reach that range, a simple one-or-other switch is not enough.

Gender is the commonest trap in .NET code that assembles labels. New {0} gives Nueva carpeta but Nuevo documento; {0} saved gives Carpeta guardada but Documento guardado. One value cannot serve both, so create a key per object (NewFolder, NewDocument) rather than a shared template.

What Manuce returns, and what it does not do

In a .resx file, Manuce translates the values of <data> elements and reads <comment> entries as context. You get the same file back: indentation, key order, quotes, comments, line endings, encoding and BOM preserved; only the values change. Accented letters and ñ are written in the file's original encoding.

Left untranslated: keys, empty values, URLs, email addresses, numbers, colours, date formats such as dd/MM/yyyy, identifiers and anything marked as non-translatable. Non-text resources stay intact, including the size and location entries stored in a WinForms form's .resx.

Each translated value is checked against the source. If a {0} or a tag goes missing or appears from nowhere and the mismatch persists, the source value is kept and the report says so, so you know exactly which strings are still in the original language.

What Manuce does not do: resize controls, rename the file, build satellite assemblies or change your code (concatenation, plural logic). Nor does it produce sworn or certified translations; if your app ships a licence agreement or terms with legal weight, have those reviewed separately.

Preparing your .resx files and checking the result

Before uploading:

• Replace concatenation such as "Delete " + name + "?" with a full value and a placeholder: Delete {0}?, which can become ¿Eliminar {0}?.
• Comment ambiguous entries: is Open a button verb (Abrir) or a status (Abierto, Abierta)? Note the register and variant you want there as well.
• Mark product names and internal codes as non-translatable.

After delivery:

1. Save the file under its culture name: Strings.es.resx for shared Spanish, or Strings.es-ES.resx / Strings.es-MX.resx for a variant. .NET falls back from es-MX to es, then to the neutral resources.
2. Read the report and deal with any strings kept in the source language.
3. Run the app with CurrentUICulture set to es-ES and walk through each screen: clipped labels, missing ¿, inconsistent register.
4. Check menu access keys: &Archivo and &Ayuda share a letter, which is why Ay&uda is common.

In practice

1. Replace concatenated strings with full values using {0} and comment any ambiguous entries.
2. Upload your .resx files: the quote reflects the exact word count of the values, and a free sample shows the quality.
3. Download the translated .resx and the report of strings left unchanged.
4. Name it Strings.es.resx (or es-ES, es-MX), rebuild and test the UI under a Spanish culture.