LINQ query result with string manipulation and regex

Question

Context

I retrieve a list of sites from a database like this:

DashboardEntities dashboardDB = new DashboardEntities();

var sites = dashboardDB.Instances
    .Select(attr => new SiteModel
        {
            server = attr.server,
            pool = attr.pool,
            url = attr.url,
            version = attr.version,
            client = ???
        })
    .ToList();

return sites;

For client, I need to get a substring from the url like this:

String client = "";

Regex rgx = new Regex(@"\.[a-z-./]+");
client = rgx.Replace(attr.url, "");

rgx = new Regex("formation-");
client = rgx.Replace(client, "");

Question

How do this string manipulation with regex into my LINQ query?

One way would be to set it to attr.url, then iterate the list after the LINQ doing the necessary replacements? — ColWhi
– ColWhi, Commented Jul 16, 2012 at 15:21

Guffa · Accepted Answer · 2012-07-16 15:27:34Z

2

You don't even need a regular expression for the second replace. You can do it as a single expression with the static overload:

client = Regex.replace(attr.url, @"\.[a-z-./]+", "").Replace("formation-", "")

answered Jul 16, 2012 at 15:27

Guffa

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GG. · Accepted Answer · 2012-07-17 12:03:19Z

2

According to Guffa and RePierre:

DashboardEntities dashboardDB = new DashboardEntities();

var sites = dashboardDB.Instances
    .Select(attr => new SiteModel
        {
            url = attr.url,
            server = attr.server,
            pool = attr.pool,
            version = attr.version,
            client = attr.url
        })
    .ToList();

sites.ForEach(attr => attr.client = Regex.Replace(attr.client, @"\.[a-z-./]+", "").Replace("formation-", ""));

answered Jul 17, 2012 at 12:03

GG.

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Joel Etherton · Accepted Answer · 2012-07-16 15:24:47Z

1

You can't in the current form you have it. There will be no known translation to SQL for the regex portion. However, you could add it on as a subsequent select once the .ToList() is called.

...   .ToList()
      .Select(
          z => z.client = new Regex(@"\.[a-z-./]+")
               .Replace(z.attr.url, "").Replace("formation-", "")
      )

Treat that as pseudo code, but that general approach should be able to get it done. Then you'd just need to set client = "" in the initial select.

Edit: As a side note, the "formation-" piece really doesn't need to be a Regex. A simple string replace should suffice there and would be faster.

answered Jul 16, 2012 at 15:24

Joel Etherton

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Comments

RePierre · Accepted Answer · 2012-07-16 15:25:36Z

Unfortunatelly, you won't be able to send the regex processing logic directly to the database; you'll need to get the url from the database and then iterate over the list to get client data from the url.

DashboardEntities dashboardDB = new DashboardEntities();  
var sites = dashboardDB.Instances 
    .Select(attr => new SiteModel 
    { 
        server = attr.server, 
        pool = attr.pool, 
        url = attr.url, 
        version = attr.version, 
        client = attr.url    // load the url for further processing
    }) 
    .ToList();
// iterate over the list and get client data from the url
sites.ForEach(ite => item.client = GetSubstring(item.client)); 
return sites;

Where the method GetSubstring encapsulates the regex processing logic.

private string GetSubstring(string url)
{
    String client = "";        
    Regex rgx = new Regex(@"\.[a-z-./]+");        
    client = rgx.Replace(attr.url, "");        
    rgx = new Regex("formation-");        
    client = rgx.Replace(client, ""); 
    return client;
}

Idan Arye · Accepted Answer · 2012-07-16 15:27:01Z

1

There might be better ways, but what about:

Regex rgx1 = new Regex(@"\.[a-z-./]+");
Regex rgx2 = new Regex("formation-");

DashboardEntities dashboardDB = new DashboardEntities();

var sites = dashboardDB.Instances
    .Select(attr => new SiteModel
        {
            server = attr.server,
            pool = attr.pool,
            url = attr.url,
            version = attr.version,
            client = rgx2.Replace(rgx1.Replace(attr.url,""),"")
        })
    .ToList();

return sites;

answered Jul 16, 2012 at 15:27

Idan Arye

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