Develop Reference

Select where IN using LINQ

Hello I'm trying to use IN condition in LINQ.
I have the following query:
select * from unitphotos Where MarketingFileTypeID = 2
AND UnitTypeID in (Select UnitTypeID from unitTypes Where PropertyID = 1)
I think I can't make it in only one LINQ query, so I did this:
var listUnitTypes = (from ut in db.unittypes
where ut.PropertyID == propertyID
select new { ut.UnitTypeID }).ToList();
var getPropertyPhotos = (from up in db.unitphotos
where listUnitTypes.Contains(up.UnitTypeID)
select up).ToList();
However, it gives me a syntax error inside Contains(up.UnitTypeID): "Argument 1: cannot convert from 'int' to 'anonymous type int UnitTypeID'
Does anyone know what I am doing wrong?
Thanks

var getPropertyPhotos = (from up in db.unitphotos
where unittypes.Any(ut => ut.PropertyID == propertyID && ut.UnitTypeId == up.UnitTypeID)
select up).ToList();
I think this should work. Haven't tried it since I don't have the db though so ymmv.
Also, yours should work if instead of select new { ut.UnitTypeID } you just put select ut.UnitTypeID

You have anonymous type here
var listUnitTypes = (from ut in db.unittypes where ut.PropertyID == propertyID select new { ut.UnitTypeID }).ToList();
And then try to use it in Linq To Entity:
var getPropertyPhotos = (from up in db.unitphotos
where listUnitTypes.Contains(up.UnitTypeID)
select up).ToList();
Seems like Linq to Entity won`t know what that type is.
So you can replace
select new { ut.UnitTypeID })
with
select { ut.UnitTypeID })
as #anakic sad before
And then create 1 query by Linq
var listUnitTypes = (from ut in db.unittypes where ut.PropertyID == propertyID select ut.UnitTypeID);
var getPropertyPhotos = (from up in db.unitphotos where listUnitTypes.Contains(up.UnitTypeID) select up).ToList();
By that you force Linq to Sql create complicated query that should be able to handle your problem.

I think that the way that you are approaching the problem forcing a sub-select is going to end up having you going back to the database more than you have to. I don't have an IDE available right now to bang out the correct LINQ syntax, but why not change your approach from thinking in terms of a SQL sub-select to that of a JOIN? Here is the SQL that I would start with and then translate that to LINQ:
SELECT p.*
FROM unitphotos p
INNER JOIN unitTypes u
ON u.UnitTypeID = p.UnitTypeID
AND u.PropertyID = 1
WHERE p.MarketingFileTypeID = 2

Building a custom|progressive query in LINQ?

I have a page with five text boxes, each one representing a field in my database table and a search button:
If I were using SQL I could build my SQL statement depending on which fields have data in them.
However, I want to use LINQ, and I'm at a loss as to how to accomplish this. For instance, take a look at the query below:
var db = new BookDBDataContext();
var q =
from a in db.Books
where a.Title.Contains(txtBookTitle) &&
a.Author.Contains(txtAuthor) &&
a.Publisher.Contains(txtPublisher)
select a.ID;
The query above will return data where all the fields match data in the table. But, what if the user didn't enter an Author in the txtAuthor field? If I were building this as a query string, I could check each field for data and add it to the query string. Since this is LINQ, I can't dynamically change the search criteria, it seems.
Any advice would be greatly appreciated!

var db = new BookDBDataContext();
var q = (from a in db.Books
where a.Title.Contains(txtBookTitle));
if(!String.IsNullOrEmpty(txtAuthor))
{
q = q.Where(a => a.Author.Contains(txtAuthor));
}
if(!String.IsNullOrEmpty(txtAuthor))
{
q = q.Where(a => a.Publisher.Contains(txtPublisher));
}
var id = q.Select(a => a.ID);

from a in db.Books
where (string.isNullorWhiteSpace(search) || a.Title.Contains(search)) &&
(string.isNullorWhiteSpace(txtAuthor) || a.Author.Contains(txtAuthor) ) &&
(string.isNullorWhiteSpace(txtPublisher) || a.Publisher.Contains(txtPublisher))
select a.ID;

Linq to Entity data model

Am trying to write a very simple select statement like below using Linq against Entity data model
trying to achieve
"Select * from SAPCostcentre where costcentermanager="mike";
Created my edmx and add a new class to write my DAO like below using linq but it doesn't like it.
public void ResourceCollection(string CostCenter)
{
string name = "Mike";
var context = new ScheduALLDAL.SAPCostCentre();
var query = from c in context.CostCentreManager where context.CostCentreManager = name select c;
var costcenter = query.ToList();
}
It throws exception "can not convert type string to bool here "context.CostCentreManager = name"
in my db design costcentermanger data type is varchar. Please some one throw me a light what am missing here or the right approach .

It should be == as you are making a Boolean evaluation. The rest of your code should be OK then :)

This is because you need to use a double equals sign (==). By using a single equals sign you are trying to assign context.CostCentreManager to "name".

It should be:
var query = from c in context.CostCentreManager
where context.CostCentreManager == name select c;
use == instead of =

var query = from c in context.CostCentreManager
where context.CostCentreManager == name
select c;

Linq to SQL: DataTable.Rows[0]["ColumnName"] equivalent

Consider this:
var query = from r in this._db.Recipes
where r.RecipesID == recipeID
select new { r.RecipesID, r.RecipesName };
How would i get individual columns in my query object without using a for-loop?
Basicly: how do I translate DataTable.Rows[0]["ColumnName"] into Linq syntax?

It's really unclear what you are looking for, as your two samples are compatible.
As close as I can figure, what you want is:
var rows = query.ToList();
string name = rows[0].RecipesName;

string name = this._db.Recipes.Single(r => r.RecipesID == recipeID).RecipesName;

This is the way to go about it:
DataContext dc = new DataContext();
var recipe = (from r in dc.Recipes
where r.RecipesID == 1
select r).FirstOrDefault();
if (recipe != null)
{
id = recipe.RecipesID;
name = recipe.RecipesName;
}

Sorry, misunderstood your question. As others are saying, you can use ToList() to get a List back. An alternative if all you need is the first one, just use:
query.First().ColumnName
or if you want to avoid an exception on empty list:
var obj = query.FirstOrDefault();
if (obj != null)
obj.ColumnName;
Original Answer (so the comment makes sense):
Use Linq to Datasets. Basically would be something like:
var query = from r in yourTable.AsEnumerable()
select r.Field<string>("ColumnName");

LINQ Query to Return multiple results

I am trying to write a textbox that will search on 5 DB columns and will return every result of a given search, ex. "Red" would return: red ball, Red Williams, etc. Any examples or similar things people have tried. My example code for the search.
Thanks.
ItemMasterDataContext db = new ItemMasterDataContext();
string s = txtSearch.Text.Trim();
var q = from p in db.ITMSTs
where p.IMITD1.Contains(s) ||
p.IMITD2.Contains(s) ||
p.IMMFNO.Contains(s) ||
p.IMITNO.Contains(s) ||
p.IMVNNO.Contains(s)
select p;
lv.DataSource = q;
lv.DataBind();

"q" in your example will be an IQueryable<ITMST>. I don't think the Datasource property of WebControl know what to do with that. try writing that line as:
lv.DataSource = q.ToList();

You can do something like this (syntax may be off )
using(var db = new ItemMasterDataContext())
{
var s = txtSearch.Text.Trim();
var result = from p in db.ITMSTs select p;
if( result.Any(p=>p.IMITD1.Contains(s))
lv.DataSource = result.Where(p=>p.IMITD1.Contains(s))
else if ( result.Any(p=>p.IMITD2.Contains(s))
lv.DataSource = result.Where(p=>p.IMITD1.Contains(s))
lv.DataBind();
}
or you might want to use this Link or this Link from MSDN.
Happy Coding!!

What you have is generally what people would do using linq. If you wanted to get more complex and use database wild cards then take a look at the SqlMethods class in System.Data.Linq.
# James Curran
You can assign the DataSource property q and it will work fine. The only different is when the query gets executed.