在文本文件中加载和访问模板变量

Question

we have a bunch of text templates that are embedded resources in our visual studio solution.

I'm using a simple method like this to load them:

    public string getTemplate()
    {
        var assembly = Assembly.GetExecutingAssembly();
        var templateName = "ResearchRequestTemplate.txt";
        string result;

        using (Stream stream = assembly.GetManifestResourceStream(templateName))
        using (StreamReader reader = new StreamReader(stream))
        {
            result = reader.ReadToEnd();
        }
        return result;
    }

So I can load the file with the above method, but how do I replace the template variables inside the file with variables I've created in my code? Is that even possible? Maybe I'm going about this all wrong...

ResearchRequestTemplate.txt:

Hello { FellowDisplayName }

You have requested access to the { ResearchProjectTitle } Project.

    Please submit all paperwork and badge ID to { ResourceManagerDisplayName }

Thanks!

Answer 1

You could use a series of string.Replace() statements.

Or you could modify the template and make use of string.Format :

Hello {0}

You have requested access to the {1} Project.

    Please submit all paperwork and badge ID to {2}

After you read in the template, insert the correct values:

return string.Format(
    result, fellowDisplayName, researchProjectTitle, resourceManagerDisplayName);

This could be a bit error prone if the template changes often, and someone's not being careful to make sure the numbering in the template matches the order of parameters being passed in.

Answer 2

Option 1 - Using Run-Time Text Templates

---

As an elegant solution you can use Run-time Text Templates . Add a new Item of Runtime Text Template to your project and and name the file ResearchRequestTemplate.tt put this content in it:

<#@ template language="C#" #>
<#@ assembly name="System.Core" #>
<#@ import namespace="System.Linq" #>
<#@ import namespace="System.Text" #>
<#@ import namespace="System.Collections.Generic" #>
<#@ parameter name="FellowDisplayName" type="System.String"#>
<#@ parameter name="ResearchProjectTitle" type="System.String"#>
<#@ parameter name="ResourceManagerDisplayName" type="System.String"#>
Hello <#= FellowDisplayName #>

You have requested access to the <#= ResearchProjectTitle #> Project.

    Please submit all paperwork and badge ID to <#= ResourceManagerDisplayName #>

Then use it this way:

var template = new ResearchRequestTemplate();
template.Session = new Dictionary<string, object>();
template.Session["FellowDisplayName"]= value1;
template.Session["ResearchProjectTitle"]= value2;
template.Session["ResourceManagerDisplayName"] = value3;
template.Initialize();
var result = template.TransformText();

This is a very flexible way and you can simply extend it, because visual studio generates a C# class for your template and for example you can create a partial class for it and put some properties in it and use typed properties simply.

Option 2 - Named String.Format

---

You can use named string format methods:

Here is an implementation by James Newton :

public static class Extensions
{
    public static string FormatWith(this string format, object source)
    {
      return FormatWith(format, null, source);
    }

    public static string FormatWith(this string format, IFormatProvider provider, object source)
    {
      if (format == null)
        throw new ArgumentNullException("format");

      Regex r = new Regex(@"(?<start>\{)+(?<property>[\w\.\[\]]+)(?<format>:[^}]+)?(?<end>\})+",
        RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.IgnoreCase);

      List<object> values = new List<object>();
      string rewrittenFormat = r.Replace(format, delegate(Match m)
      {
        Group startGroup = m.Groups["start"];
        Group propertyGroup = m.Groups["property"];
        Group formatGroup = m.Groups["format"];
        Group endGroup = m.Groups["end"];

        values.Add((propertyGroup.Value == "0")
          ? source
          : DataBinder.Eval(source, propertyGroup.Value));

        return new string('{', startGroup.Captures.Count) + (values.Count - 1) + formatGroup.Value
          + new string('}', endGroup.Captures.Count);
      });

      return string.Format(provider, rewrittenFormat, values.ToArray());
    }
}

And the usage:

"{CurrentTime} - {ProcessName}".FormatWith(
    new { CurrentTime = DateTime.Now, ProcessName = p.ProcessName });

You can also take a look at an implementation by Phil Haack .

Answer 3

You can use a simple replacement scheme using regular expressions:

var replacements = new Dictionary<string, string>() {
    { "FellowDisplayName", "Mr Doe" },
    { "ResearchProjectTitle", "Frob the Baz" },
    { "ResourceManagerDisplayName", "Mrs Smith" },
};

string template = getTemplate();    
string result = Regex.Replace(template, "\\{\\s*(.*?)\\s*\\}", m => {
    string value;
    if (replacements.TryGetValue(m.Groups[1].Value, out value))
    {
        return value;
    }
    else
    {
        // TODO: What should happen if we don't know what the template value is?
        return string.Empty;
    }   
});
Console.WriteLine(result);