LINQ and dynamic where clauses

[=?Utf-8?B?TWlrZSBDb2xsaW5z?=]

I am trying to set up a dynamic search using linq. I believe the syntax is
correct, but cannot confirm it because when I try to cast my
Session[“Employees”] from a List<to IQueryable<>, I get a cast error
“Unable to cast object of type System.Collecti ons.Generic.Lis t to type
System.Linq.IQu eryable”. Is there a way to cast List<to IQueryable<>, or is
there a different way I need to be doing this?

protected void btnSearch_Click (object sender, EventArgs e)
{
try
{
if (Session["Employees"] != null)
{
IQueryable<Busi nessLogic.Servi ces.UserProfile employees =
(IQueryable<Bus inessLogic.Serv ices.UserProfil e>)(List<Busine ssLogic.Service s.UserProfile>) Session["Employees"];

switch (ddSearchCriter ia.SelectedValu e)
{
case "UserName":
employees.Where (c =c.Username ==
txtSearchCriter ia.Text);
break;

case "Email":
employees.Where (c =c.EmailAddress ==
txtSearchCriter ia.Text);
break;

default: //LastName
employees.Where (c =c.Person.LastN ame ==
txtSearchCriter ia.Text);
break;
}

BindGrid(employ ees.Select(c =>
c).ToList<Busin essLogic.Servic es.UserProfile> ());
}
else
{
List<BusinessLo gic.Services.Us erProfileemploy ees = null;
Shared.Business Logic.UserSearc hFilter filter = new
UserSearchFilte r();

switch (ddSearchCriter ia.SelectedValu e)
{
case "UserName":
filter.Username = txtSearchCriter ia.Text;
break;

case "Email":
filter.EmailAdd ress = txtSearchCriter ia.Text;
break;

default: //LastName
filter.LastName = txtSearchCriter ia.Text;
break;
}

PagedResult<Bus inessLogic.Serv ices.UserProfil epagedResult =
SearchEmployees (filter);
employees =
pagedResult.Res ults.ToList<Bus inessLogic.Serv ices.UserProfil e>();
BindGrid(employ ees.ToList<Busi nessLogic.Servi ces.UserProfile >());
}
}
catch (ThreadAbortExc eption) { }
catch (Exception ex) { ExceptionHelper .Publish(ex); }
}

[mesut]

Re: LINQ and dynamic where clauses

Hi Mike, there are several ways of doing this. But I got this way
working...

I hope it helps,

cheers, mesut


objDataContext = DatabaseFactory .GetLinq();
List<Linq.tblCo stLocalTable;
var query = (from costing in objDataContext. tblCosts
select costing);

//the where code below (2 lines) are
replace by dynamic where
//where costing.Product ID == productID &&
//costing.Busines sUnit == businessUnit

if (productID != 0) query = query.Where(cos t =>
cost.ProductID == productID);
if (!string.IsNull OrEmpty(busines sUnit)) query =
query.Where(cos t =cost.BusinessU nit == businessUnit);

LocalTable = query.ToList();

return LocalTable;

[=?Utf-8?B?TWlrZSBDb2xsaW5z?=]

Re: LINQ and dynamic where clauses

Thanks for the reply, but I am not able to get it to work yet. Can you, or
anyone, offer some input.

Below is what I tried...also I decided that I needed to use SQLMethods.Like

List<.BusinessL ogic.Services.U serProfileemplo yees =
(List<.Business Logic.Services. UserProfile>)Se ssion["Employees"];
var query = from p in employees
select p;

switch (ddSearchCriter ia.SelectedValu e)
{
case "UserName":
query.Where(c =SqlMethods.Lik e(c.Username, "%" + txtSearchCriter ia.Text
+ "%"));
break;

case "Email":
query.Where(c =SqlMethods.Lik e(c.EmailAddres s, "%" +
txtSearchCriter ia.Text + "%"));
break;

default: //LastName
query.Where(c =SqlMethods.Lik e(c.Person.Last Name, "%" +
txtSearchCriter ia.Text + "%"));
break;
}

employees = query.ToList();

BindGrid(employ ees);


"mesut" wrote:

Hi Mike, there are several ways of doing this. But I got this way
working...
>
I hope it helps,
>
cheers, mesut
>
>
objDataContext = DatabaseFactory .GetLinq();
List<Linq.tblCo stLocalTable;
var query = (from costing in objDataContext. tblCosts
select costing);
>
//the where code below (2 lines) are
replace by dynamic where
//where costing.Product ID == productID &&
//costing.Busines sUnit == businessUnit
>
if (productID != 0) query = query.Where(cos t =>
cost.ProductID == productID);
if (!string.IsNull OrEmpty(busines sUnit)) query =
query.Where(cos t =cost.BusinessU nit == businessUnit);
>
LocalTable = query.ToList();
>
return LocalTable;
>

[=?Utf-8?B?YnJ1Y2UgYmFya2Vy?=]

RE: LINQ and dynamic where clauses

the where clause in a Linq query does not set a property, its a method
(actually an extension method) that returns another IQueryable object that
the Select method (which also return an IQueryable) can be called on. your
code is throwing away the results of the Where.




-- bruce (sqlwork.com)


"Mike Collins" wrote:

I am trying to set up a dynamic search using linq. I believe the syntax is
correct, but cannot confirm it because when I try to cast my
Session[“Employees”] from a List<to IQueryable<>, I get a cast error
“Unable to cast object of type System.Collecti ons.Generic.Lis t to type
System.Linq.IQu eryable”. Is there a way to cast List<to IQueryable<>, or is
there a different way I need to be doing this?
>
protected void btnSearch_Click (object sender, EventArgs e)
{
try
{
if (Session["Employees"] != null)
{
IQueryable<Busi nessLogic.Servi ces.UserProfile employees =
(IQueryable<Bus inessLogic.Serv ices.UserProfil e>)(List<Busine ssLogic.Service s.UserProfile>) Session["Employees"];
>
switch (ddSearchCriter ia.SelectedValu e)
{
case "UserName":
employees.Where (c =c.Username ==
txtSearchCriter ia.Text);
break;
>
case "Email":
employees.Where (c =c.EmailAddress ==
txtSearchCriter ia.Text);
break;
>
default: //LastName
employees.Where (c =c.Person.LastN ame ==
txtSearchCriter ia.Text);
break;
}
>
BindGrid(employ ees.Select(c =>
c).ToList<Busin essLogic.Servic es.UserProfile> ());
}
else
{
List<BusinessLo gic.Services.Us erProfileemploy ees = null;
Shared.Business Logic.UserSearc hFilter filter = new
UserSearchFilte r();
>
switch (ddSearchCriter ia.SelectedValu e)
{
case "UserName":
filter.Username = txtSearchCriter ia.Text;
break;
>
case "Email":
filter.EmailAdd ress = txtSearchCriter ia.Text;
break;
>
default: //LastName
filter.LastName = txtSearchCriter ia.Text;
break;
}
>
PagedResult<Bus inessLogic.Serv ices.UserProfil epagedResult =
SearchEmployees (filter);
employees =
pagedResult.Res ults.ToList<Bus inessLogic.Serv ices.UserProfil e>();
BindGrid(employ ees.ToList<Busi nessLogic.Servi ces.UserProfile >());
}
}
catch (ThreadAbortExc eption) { }
catch (Exception ex) { ExceptionHelper .Publish(ex); }
}
>

[=?Utf-8?B?TWlrZSBDb2xsaW5z?=]

RE: LINQ and dynamic where clauses

So, it seems that I do not need to cast my Session object to an IQueryable
object then...since that line does not work anyway. I can just cast it to a
list<>, then put the results of the where into an IQueryable object at that
time. Is that correct?

"bruce barker" wrote:

the where clause in a Linq query does not set a property, its a method
(actually an extension method) that returns another IQueryable object that
the Select method (which also return an IQueryable) can be called on. your
code is throwing away the results of the Where.
>
>
>
>
-- bruce (sqlwork.com)
>
>
"Mike Collins" wrote:
>

I am trying to set up a dynamic search using linq. I believe the syntax is
correct, but cannot confirm it because when I try to cast my
Session[“Employees”] from a List<to IQueryable<>, I get a cast error
“Unable to cast object of type System.Collecti ons.Generic.Lis t to type
System.Linq.IQu eryable”. Is there a way to cast List<to IQueryable<>, or is
there a different way I need to be doing this?

protected void btnSearch_Click (object sender, EventArgs e)
{
try
{
if (Session["Employees"] != null)
{
IQueryable<Busi nessLogic.Servi ces.UserProfile employees =
(IQueryable<Bus inessLogic.Serv ices.UserProfil e>)(List<Busine ssLogic.Service s.UserProfile>) Session["Employees"];

switch (ddSearchCriter ia.SelectedValu e)
{
case "UserName":
employees.Where (c =c.Username ==
txtSearchCriter ia.Text);
break;

case "Email":
employees.Where (c =c.EmailAddress ==
txtSearchCriter ia.Text);
break;

default: //LastName
employees.Where (c =c.Person.LastN ame ==
txtSearchCriter ia.Text);
break;
}

BindGrid(employ ees.Select(c =>
c).ToList<Busin essLogic.Servic es.UserProfile> ());
}
else
{
List<BusinessLo gic.Services.Us erProfileemploy ees = null;
Shared.Business Logic.UserSearc hFilter filter = new
UserSearchFilte r();

switch (ddSearchCriter ia.SelectedValu e)
{
case "UserName":
filter.Username = txtSearchCriter ia.Text;
break;

case "Email":
filter.EmailAdd ress = txtSearchCriter ia.Text;
break;

default: //LastName
filter.LastName = txtSearchCriter ia.Text;
break;
}

PagedResult<Bus inessLogic.Serv ices.UserProfil epagedResult =
SearchEmployees (filter);
employees =
pagedResult.Res ults.ToList<Bus inessLogic.Serv ices.UserProfil e>();
BindGrid(employ ees.ToList<Busi nessLogic.Servi ces.UserProfile >());
}
}
catch (ThreadAbortExc eption) { }
catch (Exception ex) { ExceptionHelper .Publish(ex); }
}