Linq Data Source - adding a where clause

Posted on 2011-09-12
Last Modified: 2012-05-12
Newby question related to LINQ and LINQ DataSource.

I have a standard ASP web page with a gridview attached to a linq data source.  A sort order is applied to the data so the most important data is generally at the top but sometimes I need to search (a very simple search)...

I have the code working by putting a hard coded string into .Where but I am confident that is NOT the best way to do this.

With User_Grid_LinqDataSource
   .Where = "First_Name.Contains(@SearchText) or Last_Name.Contains(@SearchText)"
   .WhereParameters.Add("SearchText", txtSearch.Text.Trim)
End With

The rest of the story...  I have 2 distinct searches based on a combo-box. 'Name' is shown above and 'Address' is the other one.

How do I use linq to apply different where clauses?

Question by:jongrossex
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Expert Comment

ID: 36524595

pl refer here for some quick samples:

Author Comment

ID: 36524813

Thanks. My questions was NOT clear, my fault.

I understand how to create the LINQ query but I do not understand how to associate it back with the LinkDataSource so that it is reflected in the grid.

So after I do the query like below...

var queryLondonCustomers = from cust in customers
                           where cust.City == "London"
                           select cust;

How do I associate the results with the data source so that it will be displayed on the grid.  I assume it is simple but I can not find the answer... or is there a better way to think about this.


LVL 83

Expert Comment

ID: 36526202
Try using the Where property of the LinqDataSource itself to do the filtering
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Author Comment

ID: 36527153
We are getting closer...  but from the above link I do not want my query coded in a string.

The following code attaches linq data to a gridview

Dim db As New SjuDatalassesDataContext
Dim searchText As String = txtSearch.Text.Trim
Dim userList = From u In db.vUser Where u.First_Name.Contains(searchText) Select u
grid.DataSourceID = Nothing
grid.DataSource = userList

How do I either
- tell the LinqDataSource 'control' to execute the query from the above Linq command
- attached userlist to the LinqDataSource 'control'


Expert Comment

ID: 36527809

can you give a try to the select property of the linqdatasource control

Linqdatasource control is meant to perform the linq operations..... hence it comes with all required properties and methods to perform linq operations... I am not sure why you want to deviate from this...

Author Comment

ID: 36529238

What I am trying to get away from is a string for the where clause
   .Where = "First_Name.Contains(@SearchText) or Last_Name.Contains(@SearchText)"

If my data model changes I do not find out till runtime

Does the 'linqdatasource' have a property that allows me to add a link command?  For example:
From u In db.vUser Where u.First_Name.Contains(searchText) Select u
I have looked and did not see any such functionality.

Thanks for your help

Expert Comment

ID: 36530384
no you can't do that...
LVL 83

Accepted Solution

CodeCruiser earned 500 total points
ID: 36531946

Author Comment

ID: 36533903
That seems exactly what I was looking for.  I will give it a try tomorrow.

Always enjoy Scott Gu's blogs.
LVL 83

Expert Comment

ID: 36570193
Any Luck?

Author Comment

ID: 36570316
Sorry for the delay... that was perfect.

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