Define the CultureInfo of the format

[ricardona]

We are using crozone/FormatWith to fill mail templates. These email templates must be sent in Spanish. However when trying to format the dates they appear in English.

Is there a mechanism to define the CultureInfo of the format?

            var template = "{d:dddd, MMMM dd, yyyy}";

            var stringDictionary = new Dictionary<string, object>
            {
                { "d", new DateTime(2025, 12, 31, 5, 10, 20) },
            };
            var result = template.FormatWith(template, stringDictionary);

            Assert.AreEqual("Wednesday, December 31, 2025", result);

Thanks in advance.

[crozone]

Hi @ricardona, unfortunately there is currently no way to explicitly set the CultureInfo (or more generally, the IFormatProvider) while calling FormatWith. However, this is something I will look at adding in version 4.0.

In the meantime, I can see two possible workarounds:

1. Format the date before passing it to format with

        // Get Spanish IFormatProvider
        IFormatProvider formatProvider = CultureInfo.CreateSpecificCulture("es");
   
        var template = "{d}";
   
        var stringDictionary = new Dictionary<string, object>
        {
            { "d", new DateTime(2025, 12, 31, 5, 10, 20).ToString("dddd, MMMM dd, yyyy", formatProvider) },
        };
        var result = template.FormatWith(stringDictionary);
   

2. Set the current culture before calling FormatWith

        CultureInfo previousCulture = CultureInfo.CurrentCulture;
   
        // Set current culture to Spanish
        CultureInfo.CurrentCulture = CultureInfo.CreateSpecificCulture("es");
   
        var template = "{d:dddd, MMMM dd, yyyy}";
   
        var stringDictionary = new Dictionary<string, object>
        {
            { "d", new DateTime(2025, 12, 31, 5, 10, 20) },
        };
        var result = template.FormatWith(stringDictionary);
   
        // Reset current culture back
        CultureInfo.CurrentCulture = previousCulture;
   

I hope one of these is suitable enough for now.

[crozone]

@ricardona I've just remembered the third (and probably best) way to do this using FormatWith v3: Using FormattableWith()

// Get Spanish IFormatProvider
IFormatProvider formatProvider = CultureInfo.CreateSpecificCulture("es");

var template = "{d:dddd, MMMM dd, yyyy}";

var stringDictionary = new Dictionary<string, object>
{
    { "d", new DateTime(2025, 12, 31, 5, 10, 20) },
};
var result = template.FormattableWith(stringDictionary).ToString(formatProvider);

Output: "miércoles, diciembre 31, 2025"

This uses FormatWith to create an intermediate FormattableString, which can then be formatted using ToString(IFormatProvider). This is clean and I recommend this over the above two workarounds.