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How to create dynamic Multiple And linq conditions in foreach loop

if (rowCount == 1)
{
query =
(from x in partJoinTableRepository.GetPartJoinQuery()
join y in partRepository.GetPartsQuery() on x.PartId equals y.Id
join z in partProductTypeReposiotry.GetPartProductTypesQuery() on x.PartId equals z.PartId
where y.IsSkipped == 0 && (y.IsDisabled != "Y" || y.IsDisabled == null) && z.CreatedDate == x.CreatedDate
&& x.CreatedDate == Convert.ToDateTime(fromDate) && cpaclassids.Contains(x.ProductTypeId.ToString())
select x).Cast<PartJoinTable>().AsQueryable();
predicate = PredicateBuilder.True(query);
}
else
{
query = query.Join(partJoinTableRepository.GetPartJoinQuery(), "PartID", "PartID", "inner", "row1", null).Cast<PartJoinTable>().AsQueryable();
// predicate = PredicateBuilder.True(query);
} //query contains multiple dynamic inner joins
//repids contains the list ,I used the predicate builder for the linq to create AND Queries
foreach(var item in repids)
{
predicate = PredicateBuilder.True(query);
if (typeid == "3")
{
predicate = predicate.And(z => ids.Contains(z.ProductTypeId.ToString()) &&
z.CreatedDate == Convert.ToDateTime(fromDate));
}
}
var count = query.Where(predicate).Distinct().Count();
the above line is taking long time to execute,ids contains the lists and query contains the linq query.basically I need to form a multiple "AND" conditions
//The Query is taking lot of time to execute and multiple and conditions are not working

Remove ToList to improve performance. Because ToList execute your query and retrieve object list to memory. But you need only count. you don't need objects.
var count = query.Where(predicate).Distinct().Count();

If I understood you right, your problem is that this query has a long running time. Let's see your code in the last line:
var count = query.Where(predicate).Distinct().ToList().Count();
In LINQ to SQL (and to entities), your query doesn't execute thought you use ToList(), ToArray() etc.. For example, consider the following query:
var strings = Db.Table
.Where((string s) => s.Contains("A")) // Will convert to something like WHERE s LIKE '%A%'
.Select(s => s.ToUpper()) // Will convert to something like SELECT upper(s)
.ToList(); // Here the query sends to the DB and executes
The final query is SELECT upper(s) FROM [Table] WHERE s LIKE '%A%'.
In you case, first you send the query to the DB and get all the objects corresponding to the condition (.Where()), and then get their count inside your app.
Instead, if you'll get from the DB only the count, the query will be faster:
var count = query.Where(predicate).Distinct().Count(); // No .ToList()! Here, .Count() executes the query.

Non-mandatory fields in the search

I have this piece of the code intended to search a database. A user should have 3 options here: to type surname only, the first name and the user can search using both of them - surname and the first name.
This code retrieves the records from my db if I provide both strings - surname and the first name. But if I type only one of them, my resulting list is always empty.
var query = from x in db.people
where (txtSurname == null || x.Surname== txtSurname.Text)
&& (txtFirstName == null || x.FirstName == txtFirstName.Text)
select x;
var data = query.ToList();
peopleBindingSource.DataSource = data;

Remember that an Entity Framework query doesn't get sent to the database until you materialise the data wth ToList or iterating over it for example. This means you can build up the query in code like this:
var query = db.people.AsQueryable();
if(!string.IsNullOrEmpty(txtSurname.Text))
{
query = query.Where(p => p.Surname == txtSurname.Text);
}
if(!string.IsNullOrEmpty(txtFirstName.Text))
{
query = query.Where(p => p.FirstName == txtFirstName.Text);
}
peopleBindingSource.DataSource = query.ToList();

Make a LINQ query dynamic to bring back all rows or only rows with a link to a lookup table?

I have a query that returns a list of currencies and joins to a lookup table. The result is then put into a class object (which works fine):
var queryforobject = from x in db.CurrencyExchangeRates.AsNoTracking()
join c in db.CurrencyTypes.AsNoTracking() on x.CurrencyTypeID equals c.ID
orderby x.ID
select new CurrencyExchangeRateObject
{
ID = x.ID,
CurrencyID = c.ID,
Currency = c.Description,
ExchangeRate = x.ExchangeRate,
LastEditedDate = x.LastEditedDate,
LastEditedBy = x.LastEditedBy,
Active = x.Active
};
I want to make this more dynamic, so if no CurrencyTypeID is supplied then it will return the full list (as it does already) - otherwise if a CurrencyTypeID is supplied it will only show where X.CurrencyTypeID = ID.
Something along the lines of an inline if?

There are a few options for filtering the query based on CurrencyTypeID if a search value (named currencyTypeID in this answer) is supplied, but return all data if no currencyTypeID is supplied.
First option: You could add a where clause to your existing query expression. The WHERE clause below will return every record in the data set if null is passed in for the currencyTypeID variable, otherwise it will filter the results.
from x in db.CurrencyExchangeRates.AsNoTracking()
join c in db.CurrencyTypes.AsNoTracking() on x.CurrencyTypeID equals c.ID
where (currencyTypeID == null || x.CurrencyTypeID == currencyTypeID)
orderby x.ID
select new CurrencyExchangeRateObject {
ID = x.ID,
CurrencyID = c.ID,
Currency = c.Description,
ExchangeRate = x.ExchangeRate,
LastEditedDate = x.LastEditedDate,
LastEditedBy = x.LastEditedBy,
Active = x.Active
};
Alternatively: Since queryforobject is of type IQueryable<T>, you can use LINQ's fluent API to append a WHERE clause to the query inside an if statement. You need to be more careful about timing on this one though as it needs to be done before you force evaluation of the IQueryable with a foreach loop, .ToList(), .Select() or other LINQ methods that force evaluation.
if(currencyTypeID != null)
queryforobject = queryforobject.Where(cerObj => cerObj.CurrencyID == currencyTypeID);

How to use Linq query Result in OrderBy?

Here i had scenario to get the data in date wise of this month(Present month)
Excepted Result
Date_time sum(collection.amountreceived ) Sum(bank_deposit.depositamount)
1/07/2014 2000 1000
2/07/2014 3000 3000
Schema
bank_deposit
agentid (nvarchar(30))
depositamount (DECIMAL(10,0))
date_time (TIMESTAMP)
collection
customeridn (varchar(30))
amountreceived (DECIMAL(10,0))
date_time (TIMESTAMP)
agentid (nvarchar(30))
Here I used union to get the datetime column data in one column
var unionDateColumn = ((from agent in db.collections select agent.Date_Time)
.Union(from u in db.bank_deposit select u.Date_Time)).ToList();
How can i use this unionDateColumn data for orderby and to get expected output?
Below is query for sum of amount but here my issue is how to
var model = (from coll in db.collections.Where(e => e.AgentID == item.AgentID)
let depositedAmount = db.bank_deposit.Where(d => d.AgentID == item.AgentID ).Sum(c => c.DepositedAmount) == null ? 0
: db.bank_deposit.Where(d => d.AgentID == item.AgentID).Sum(x => x.DepositedAmount)
let collectionAmount = db.collections.Where(c => c.AgentID == item.AgentID).Sum(c => c.AmountReceived) == null ? 0
: db.collections.Where(v => v.AgentID == item.AgentID).Sum(m => m.AmountReceived)
select new GetBalanceAmount
{
DepositedAmount = depositedAmount,
CollectionAmount = collectionAmount
});

I assume you want to order the result by date_time
var result = unoinDateColumn.OrderBy(t=>t.Date_Time).ToList().;

Why FirstOrDefault ? i asume you want every row.
Sajeetharan's example:
var result = unoinDateColumn.OrderBy(t=>t.Date_Time).ToList();
result is the same as "select * from unionDateColumn order by DateTime"
Your example:
model.ToList().OrderByDescending(unoinDateColumn).FirstOrDefault();
is the same as "Select * from model orderby unionDateColumn"
May i ask why you are handling each column seperately? insted of in one large array ?
Handle it in one array, and do like this model.OrderByDescending(x => x.Date_Time);
it will affect the object model and order it like this model = model.sortedBy(model.Date_Time);

Linq Select Clause w/ Unknown Number of Fields

I have a linq query in which I need to be able to select an variable number of fields from a datatable. I do know all of the fields that could be included, but only two will for sure be in the datatable. I also will know which fields are included in the datatable (it will just be different depending on the user's selections). Right now I set up something like this:
var query = from item in dt.AsEnumerable()
group item by item.Field<string>("ID") into g
select new
{
ID = g.Key, //required
Status = g.Min(i => dostuff(i,"Status")), //not required
Disc = g.Min(i => dostuff(i,"Disc")), //not required
Loc = String.Join<string>(",", from i in g select i.Field<string>("Loc")) //required
};
dostuff(DataRow i,string field)
{
try
{
return i.Field<string>(field);
}
catch
{
return null;
}
}
So dostuff basically is just checking whether or not that field exists in the dataset, and then I would just need to ignore the non-existant fields when working with the query results, which would not be too difficult. However, it seems like there is probably a better way to do this, but I've had a tough time finding anything via Google about using a dynamic select clause.

You could do it with dynamic type (nb, I did not test so this might have typos.):
var query =dt.AsEnumerable().GroupBy(item => item.Field<string>("ID"))
.Select(g => {
dynamic t = new System.Dynamic.ExpandoObject();
if (g.Table.Columns.Any(c => c.ColumnName == "Status"))
t.Status = g.Field<string>("Status");
if (g.Table.Columns.Any(c => c.ColumnName == "Disc"))
t.Disc = g.Field<string>("Disc");
t.ID = g.Key;
t.Loc = String.Join<string>(",",g.Select(i => i.Field<string>("Loc")));
return t;
}