[stringtemplate-interest] Merge email using StringTemplate.NET through multiple passes

[Terence Parr]

Hi, when you call toString() you are destroying all possible attribute  
information and getting a string. why are you evaluating twice? just  
set the attributes that you want and then do a single toString.
Ter
On Nov 15, 2008, at 4:18 PM, Tam Ly wrote:

> I am new to StringTemplate.NET and appreciate your help. I am trying  
> to use StringTemplate.NET (antlr.runtime.dll 2.7.7.1 &  
> StringTemplate.dll 3.0.1.21733) to generate html emails to be sent  
> from my web site. I am using a database to store my content as  
> followed:
>
> ResourceName            ResourceValue
> -----------------       ----------------------------------
> EmailHeader             <center>If you have trouble viewing this  
> email, <a href='https://www.chaseidprotect.com/displayEmail.aspx?mid=$MemberId$&eid=$EmailDocumentId$' 
> >click here</a></center><br />
>                        <img src='https://www.chaseidprotect.com/images/companylogo.jpg' 
>  alt='Chase' />
> EmailWelcome            $EmailHeader$<br />
>                        Dear $FirstName$ $LastName$,
>                        Hello world! This is a test of StringTemplate!
> There is another table that tells me that EmailWelcome resource uses  
> EmailHeader resource. For performance reasons, I want to cache my  
> resource so I have to merge data in 2 passes:
> 1st pass: Merge the value of EmailHeader to EmailWelcome
> 2nd pass: Merge my member and email template data to EmailWelcome
> Here's the sample code:
>       private void button2_Click(object sender, EventArgs e)
>       {
>           string emailHeader = "<center>If you have trouble viewing  
> this email, <a href='https://www.chaseidprotect.com/displayEmail.aspx?mid=$MemberId$&eid=$EmailDocumentId$' 
> >click here</a></center><br /><img src='https://www.chaseidprotect.com/images/companylogo.jpg/companylogo.jpg' 
>  alt='Chase' />";
>           string emailWelcome = "$EmailHeader$<br />Dear $FirstName$  
> $LastName$, <br />Hello world! This is a test of StringTemplate!";
>           // 1st pass, merge resource only because we do not have  
> member or email template data yet
>           StringTemplate emailContent = new  
> StringTemplate(emailWelcome, typeof(DefaultTemplateLexer));
>           emailContent.SetAttribute("EmailHeader", emailHeader);
>           Debug.WriteLine(emailContent.ToString());
>           // 2nd pass, merge member and email template data when an  
> email is queued
>           StringTemplate emailMerged = new  
> StringTemplate(emailContent.ToString(), typeof(DefaultTemplateLexer));
>           emailMerged.SetAttribute("MemberId", 241);
>           emailMerged.SetAttribute("EmailDocumentId", 1);
>           emailMerged.SetAttribute("FirstName", "Tam");
>           emailMerged.SetAttribute("LastName", "Ly");
>           Debug.WriteLine(emailMerged.ToString());
>       }
>
> Because I do not have my member's and email template data: MemberId,  
> FirstName, LastName and EmailDocumentId at the 1st pass, I have to  
> merge my member and email template data at the 2nd pass.
> Unfortunately, my member's attributes: $FirstName$ and $LastName no  
> longer exist in the EmailWelcome after my 1st pass of merging.
> It looks like StringTemplate evaluates the attribute to emptry  
> string if I don't pass in the value the first time. Is there a way  
> to tell StringTemplate to pass through an attribute if a value is not
> passed in instead of evaluating to empty string?
>
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