Universal IQueryable Search Usable by Linq-to-SQL and Linq-to-Entities

ever since Linq came out, I have been improving my simple 'google-like' searches; I think I found the holy grail

UPDATE 05/12/2009 - I have done a ton of updates to the class using Reflection, and a new version which is much more usable and simple will be out in the next day or two.

The 'quick search' is a great tool. Google has shown us that searching with one single, universal search field is the way that people prefer to search. Anyone who has worked with Linq for any amount of time knows this is possible, but it requires a lot of hard-coding and a long jumble of 'where' statements. This class will allow you to run a universal 'google-like' search on any IQueryable.

Now what I am going to show you here was a breakthrough to me, and it has made my life a whole lot easier. It may not be the best way to do this, but it is the best/fastest way I could figure out (hint: I am always looking for improvements), and it is totally portable for *any* multi-column IQueryable collection, plus it does multiple relations as well!

dynamic linq

First of all, this uses the System.Linq.Dynamic dll that was released a while back - it writes a dynamic query each search run, so this was necessary in my approach. If you do not have it, you can get it here: http://msdn2.microsoft.com/en-us/vcsharp/bb894665.aspx.

data for the example

For this example, I am going to be working with Linq-to-SQL, but this works just as well with Linq-to-Entities and have used it in both types of projects. Here is the dummy data I am using for the demo:
CREATE TABLE dbo.category (
category_name VARCHAR(MAX)

INSERT INTO dbo.category VALUES ('ninja');
INSERT INTO dbo.category VALUES ('pirate');
INSERT INTO dbo.category VALUES ('zombie');
INSERT INTO dbo.category VALUES ('weakling');

CREATE TABLE dbo._user (
first_name VARCHAR(MAX),
last_name VARCHAR(MAX),
email_address VARCHAR(MAX),
category_id INT REFERENCES category(category_id)

  ('stan', 'naspinski', 'stan@mailinator.com', 2);
  ('sara', 'ortbals', 'hotchick@yahoo.com', 1);
  ('rj', 'russell', 'punk@ilovedudes.com', 4);
  ('brian', 'pond', 'captweaksauce@ilovedudes.com', 4);
  ('idaho', 'edokpayi', 'idaho@yahoo.com', 1);
  ('phil', 'robles', 'crazyphil@hotmail.com', 3);
  ('jose', 'meza', 
    'iwishiwasasstrongasstan@gmail.com', 2);

Just a table of users with a referenced table of categories so I can demonstrate the multi-level search. Here is what my dbml looks like:

quick example

Now, say I want to do a universal search in all the fields for the word 'stan', it is as simple as this:
string[] columns_to_search = {"first_name", "last_name", "email_address", "category.category_name"};
string[] search_terms = {"stan"};
var search_results = new dbDataContext()._users.Search(columns_to_search, search_terms); 

All I did was specify which columns to include in the search, and what terms to search for; doesn't get much simpler than that. This is the simplest approach/overload, so you can get much more detailed if you want, and I will get into that later, but here you can see how powerful and simple this is. Here are the results when bound to a GridView:

search for 'stan'
search for 'stan'

This simply runs through the columns you specify and runs a Contains() against each field; if the keyword is found in one of those fields, it is considered to be a valid record. As you can see, the email address of of record 7 has the word 'stan' in it as well as the name and email address of record 1. Now if I narrow the search by adding another search term: 'pirate' you will see it narrows down the search to just one:

search for {'stan', 'pirate'}
search for 'stan', 'pirate'

Now you can not see 'pirate' in this GridView as it is just an auto-generated GridView, but 'pirate' is the value of the 'category.category_name' record 2 which is referenced in the last column (chopped off a bit); so you can see how easy it is to use relations with this tool.

what is happening

It is pretty simple what is happening. For each object that is passed in the 'keywords' the IQueryable is whittled down so only the ones that 'pass' remain:

searching with 'stan' and 'pirate' (psuedocode)
IQueryable results;
results = dbDataContext._users.Where(any_of_the_specified_fields.Contains(first term));
results = results.Where(any_of_the_specified_fields.Contains(second_term));
results = results.Where(any_of_the_specified_fields.Contains(third_term));
...and so on...

Note that this only does a single db call to get the first IQueryable (in the case your IQueryable is from a database), once that one is in memory, all searches are done against it, so it is pretty fast.

the search textbox

Now that is all very simple, but rarely are your searches going to be hard-coded, so it would be simple to code in a button handler to search through a specified textbox with something like this:
protected void btnSearch_Click(object sender, EventArgs e)
  char[] search_delimiters = { ',', ' ', ';', '+' };
  string[] columns_to_search =  {"first_name", "last_name", "email_address", "category.category_name"};
  gvSearch.DataSource = new dbDataContext()._users
    .Search( columns_to_search, txtSearch.Text.Split(search_delimiters));

Pretty basic stuff there, you could also get your columns to search from a user interface like a bunch of CheckBoxes or a ListBox control.

getting more specific

If you look into the code, you can see it gets more and more specific the more you drill down into it. With the above overload, it assumes you are using all string comparable fields and all of your inputs are strings. The class's abilities do not stop there, and can get more and more specific. Say you had a massive table with the following fields: int named 'ID', DateTime named 'birthday', text named 'name' and bool named 'male'. If you simply tried the above overload with that, it would error as the types int, DateTime and bool do not have Contains() methods. But, if you specify name/type, you can use this to great advantage:
Dictionary ColumnNamesAndTypes =  new Dictionary<string, Type>();
ColumnNamesAndTypes.Add("ID", typeof(int));
ColumnNamesAndTypes.Add("first_played_videogames", typeof(DateTime));
ColumnNamesAndTypes.Add("name", typeof(string));
ColumnNamesAndTypes.Add("male", typeof(bool));

object[] search_for = {18, 25, DateTime.Parse("12/08/1981"), true, "a","b","c" };

var search_results = largeTable.Search(ColumnNamesAndTypes.ToArray(), search_for);

Now, since the Search now knows the types, it will only run valid types against the fields; for example, the 'true' object will only be run against the 'male' field, as it is the only 'bool' field, the values '18' and '25' are ints, so they will only be compared to the 'age' field of type 'int'. So, what this search would do is return all the people in the IQueryable 'largeTable' that are ages 18 and 25, who 'first_played_videogames' on 12/08/1981, that have an a,b or c in their names who are male. Now I know you can easily write these queries in Linq yourself, but if somehting changes, you are hardcoding a search change that is easy to screw up, this does it all for you.

parsing varying strings

Now there is a little more difficulty with attempting to pass in data through the magical 'google-like' single search box, but it really isn't that hard, check this out:
protected object[] parseSearchString(string search_string)
    int obInt;
    DateTime obDt;
    bool obBool;

    char[] search_delimiters = { ',', ' ', ';', '+' };
    List<object> obs = new List<object>();

    foreach (string s in search_string.Split(search_delimiters))
        if (Int32.TryParse(s, out obInt)) obs.Add(obInt);
        else if (DateTime.TryParse(s, out obDt)) obs.Add(obDt);
        else if (bool.TryParse(s, out obBool)) obs.Add(obBool);
        else obs.Add(s); // else it's a string
    return obs.ToArray();

Now I obviously didn't go through all the types there, but you get the idea. This takes in a string from a textbox and tries to parse it out to the more specific types before it defaults to a string. Now you might run into conflicts when you want to use integers as strings and such, but if you are this far in this post and still understanding things, I am sure you can figure out a way to code around that. Going back to the original example, now if I wanted to search the '_users' table for either 'category_id' (which is an integer) or the name of that category, I would just use the following:
protected void btnSearch_Click(object sender, EventArgs e)
  Dictionary<string, Type> columns_to_search = new Dictionary<string, Type>();
  columns_to_search.Add("category_id", typeof(Int32));
  columns_to_search.Add("category.category_name", typeof(string));
  gvSearch.DataSource = new dbDataContext()._users
    .Search( columns_to_search, parseSearchString(txtSearch.Text));

And as you can see that uses the above 'parseSearchString' so if I enter in '1', it is searched as in Int32:
search for '1'

And if I type in 'ninja' is is searched with a 'string' (ninja is the string value of category_id 1):
search for 'ninja'

that's it

I am hoping that at least a few of you can decipher my ramblings... hopefully you can see how this can be useful to you, and with any luck, it will save you some time and headaches. If people are interested, I can go into the code and how it works, but for now I will just leave you with the source (I even wrote comments... something I am horrible at). I am hopeing someone knows how to get the fields/types automatically from a generic IQueryable so this can be made even better - if you know how to do that, please share!!!

Comments (1) -

  • The QueryableSearch is a great additional to LINQ.  I have a question though.  In your example you perform a search from the user table and can include category.category_name.  What if you wanted to search the other way around, i.e.

    var search_results = new dbDataContext().category.Search(columns_to_search, search_terms);

    When I tried this it errors out in the ParseMemberAccess method because it the type is System.Data.Linq.EntitySet<ObjectType> but the column name i specified is a property from ObjectType not EntitySet.  I'm still new to LINQ so if you could help me out or maybe point me in the right direction that would be awesome.

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