A very basic general-purpose substitution-based template engine.

Main.cs

public void Main()
{
    var template = "Hello {{Name}}, how are you?";
    var model = new { Name = "Alice" };

    var output = TemplateEngine.Execute(template, model);
    // Output: "Hello Alice, how are you?"
}

TemplateEngine.cs

public class TemplateEngine
{
    /// <summary>
    /// Parses the template and fuses it with the data model.
    /// </summary>
    /// <param name="template">The template which is acted upon.</param>
    /// <param name="model">The model which is fed to the template.</param>
    /// <exception cref="FormatException">Property not found in model.</exception>
    /// <returns>A string generated from the template.</returns>
    public static string Execute(string template, object model)
    {
        var modelType = model.GetType();
        
        foreach (var match in Regex.Matches(template, @"{{\w+}}"))
        {
            var propertyName = match.ToString().Trim(new[] {'{', '}'});
            var property = modelType.GetProperty(propertyName);
        
            if (property == null)
            {
                throw new FormatException("Property '" + propertyName + "' does not exist in model.");
            }
        
            template = template.Replace(match.ToString(), property.GetValue(model, null).ToString());
        }
    
        return template;
    }

    /// <summary>
    /// Parses the template and fuses it with the data model.
    /// </summary>
    /// <param name="template">The template which is acted upon.</param>
    /// <param name="model">The model which is fed to the template.</param>
    /// <exception cref="KeyNotFoundException">Property not found in model.</exception>
    /// <returns>A string generated from the template.</returns>
    public static string Execute(string template, IDictionary<string, string> model)
    {
        foreach (var match in Regex.Matches(template, @"{{\w+}}"))
        {
            var propertyName = match.ToString().Trim(new[] { '{', '}' });

            template = template.Replace(match.ToString(), model[propertyName]);
        }

        return template;
    }
}