Full Text Search with LINQ

Question

I am trying to implement a search function where the results could be populated to a Gridview. I am using LINQ to query my db in c#.

The problem I am trying to figure out is, if the user want to search through multiple columns/fields with more than one search term, then how do I do that? So instance if I search a table with these 3 fields and I had some data like: > firstName | lastname | players# >>1. Michael | Jordan | 12 >>2. Michael | Jordan | 24 >>3. Michael | Jordan | 45 >>4. DeAndre| Jordan | 6 >>5. Jerome| Jordan | 44 >>6. Jordan| Sparks| 88

Now if I search for Jordan I get everything:

If I search Michael Jordan than I should get row #s 1,2,3 back.

If I search Jordan Sparks 88 than I should row # 6 back.

So my problem is I don't know where in the table the search term may be so I must search all columns/fields. In my current code, I have something where I go through each column/field name and use the Contains() then || ("or"), but it only works for 1 search term.

Is there an elegant and easy way to search and filter through a whole linq table so that the list is minimized? From there I will add that result to a datasource and then bind it.

@Sphinxxx I am using a typical gridview. It looks like this:

    <asp:GridView ID="GridView" runat="server" AllowSorting="True" PagerStyle-Mode="NumericPages"
                                AutoGenerateColumns="false" Width="100%" CssClass="gridView" OnPageIndexChanging="GridView_PageIndexChanging"
                                AllowPaging="True"  DataKeyNames="idPlayersList" OnRowCommand="GridView_RowCommand"
                                OnRowEditing="GridView_RowEditing" OnRowCancelingEdit="GridView_CancelEditRow"
                                OnRowUpdating="GridView_UpdateRow" OnRowDataBound="GridView_RowDataBound">
                                <RowStyle CssClass="rowStyle"></RowStyle>
                                    <asp:BoundField DataField="FirstName" HeaderText="First Name" SortExpression="FirstName" />
                                    <asp:BoundField DataField="LastName" HeaderText="Last Name" SortExpression="LastName" />
<asp:BoundField DataField="PlayersNumber" HeaderText="Players Number" SortExpression="PlayersNumber" />
<asp:TemplateField HeaderText="Team" SortExpression="Team">
                                    <EditItemTemplate>
                                        <asp:DropDownList ID="ddlTeam" runat="server" CssClass="dropdown" AutoPostBack="True"
                                            AppendDataBoundItems="true" DataTextField="TeamName" DataValueField="idTeam">
                                        </asp:DropDownList>
                                    </EditItemTemplate>
                                    <ItemTemplate>
                                        <asp:Label ID="lblTeam" runat="server" Text='<%# Bind("TeamName") %>'></asp:Label>
                                    </ItemTemplate>
                                </asp:TemplateField>

My current search function looks something like this:

/**
* This method is for button search functionality 
* 
*/
protected void btnSearch_Click(object sender, EventArgs e)
{

    // Call to Entity Model Framework
    DBModel.DBEntities context = new DBModel.DBEntities();
    
    string[] searchTerms = txtSearch.Text.Trim().Split('&');

//Prepare to build a "players" query:
IQueryable<DBModel.playersList> playersListQuery = context.playersLists;

foreach (var term in searchTerms)
{
    //Refine our query, one search term at a time:
    playersListQuery = playersListQuery.Where(p => p.isDeleted == false && (p.FirstName.Contains(term.Trim()) ||
                                           p.LastName.Contains(term.Trim()) ||
                                           p.PlayersNumber.Contains(term.Trim()) ||
                                           p.Team.Name.Contains(term.Trim())));
}

//Now we have the complete query. Get the results from the database:
var filteredplayersList = playersListQuery.Select(s => new
                                           {

                                               idPlayersList = s.idPlayersList,
                                               FirstName = s.FirstName,
                                               LastName = s.LastName,
                                               PlayersNumber  = s.PlayersNumber,
                                               TeamName  = s.Team.Name
                                            }).ToList();


GridView.DataSource = filteredplayersList; //Connecting query to the datasource Gridview
GridView.DataBind();  //Binding Gridview
}

Answer 1

Luckily, creating multiple ANDs (one for each search term) is easy in Linq2SQL - just keep adding .Where(.. to your query:

string[] searchTerms = "Jordan Sparks 88".Split(' ');

using (var dc = new MyDataContext())
{
    //Using DataContext.Log is handy 
    //if we want to look at Linq2SQL's generated SQL:
    dc.Log = new System.IO.StringWriter();

    //Prepare to build a "players" query:
    IQueryable<Player> playersQuery = dc.Players;

    //Refine our query, one search term at a time:
    foreach (var term in searchTerms)
    {
        //Create (and use) a local variable of the search term
        //to avoid the "outer variable trap":
        //http://stackoverflow.com/questions/3416758
        //http://stackoverflow.com/questions/295593
        var currentTerm = term.Trim();
        playersQuery = playersQuery.Where(p => (p.isDeleted == false)
                                                &&
                                               (p.FirstName.Contains(currentTerm) ||
                                                p.LastName.Contains(currentTerm) ||
                                                p.PlayersNumber.Contains(currentTerm) ||
                                                p.Team.Name.Contains(currentTerm))
                                            );
    }

    //Now we have the complete query. Get the results from the database:
    var filteredPlayers = playersQuery.Select(p => new
                                                   {
                                                       p.idPlayer,
                                                       p.FirstName,
                                                       p.LastName,
                                                       p.PlayersNumber,
                                                       TeamName = p.Team.Name
                                                   })
                                      .ToArray();

    //See if the generated SQL looked like it was supposed to:
    var sql = dc.Log.ToString();
}

Answer 2

If you just need to use the Contains condition for all the properties, what you can do is to encapsulated all the properties that you need into a single one, then you can apply the LINQ expression with fewer fields, it would look cleaner.

public class Player
{
    public string SearchField { get => string.Format("{0}{1}{2}{3}",FirstName,LastName,PlayersNumber,Team); }

    public string FirstName {get; set;}

    public string LastName {get; set;}

    public string PlayersNumber {get; set;}

    public string Team {get; set;}
}

Even better I would recommend you to set the SearchField in the constructor when you create your object instance which will improve performance avoiding to create a substring for every invocation.

public string SearchField { get; private set; }

public Player(string firstName, string lastName, playersNumber, string team)
{
    FirstName = firstName;
    LastName = lastName;
    PlayersNumber = playersNumber;
    Team = team;
    SearchField = string.Format("{0}{1}{2}{3}",firstName,lastName,playersNumber,team);
}

Then you just filter by SearchField property

 foreach (var term in searchTerms)
 {
     var currentTerm = term.Trim();
     playersQuery = playersQuery.Where(p => p.isDeleted == false && 
                                            p.SearchField.Contains(currentTerm));
 }

Now you have a LINQ expression with fewer fields which gets you the exact same result set.

One more thing I just saw that you mentioned you were working with LINQ to SQL query, you could apply the same approach by creating a Computed Column in your SQL table that concatenate the value from multiple columns, you can do this since SQL Server 2012.

Hopefully someone finds this solution helpful.

Regards!