Develop Reference

Comparison with multiple Where clause in LINQ C#

I have two DataTables:
DataTable dtCatalogFromMySql;
DataTable dtDataForExistingProducts;
dtCatalogFromMySql
Id | productname | barcode | pricesell| type
---+--------------+----------+----------+------
1 | Abz | 123 | 2.01 | RS // different product name
2 | Abd | 122 | 8.90 | RS // different price
3 | Abx | 125 | 21.00 | WS // both different
4 | Abf | 124 | 2.11 | RS
5 | Abg | 126 | 8.01 | WS
6 | Abh | 127 | 60.23 | RS
7 | Abi | 128 | 9.10 | RS
dtDataForExistingProducts
Id | productname | barcode | pricesell| type
---+--------------+----------+----------+------
1 | Abc | 123 | 2.01 | RS
2 | Abd | 122 | 3.90 | RS
3 | Abe | 125 | 23.00 | WS
4 | Abf | 124 | 2.11 | RS
5 | Abg | 126 | 8.01 | WS
6 | Abh | 127 | 60.23 | RS
7 | Abi | 128 | 9.10 | RS
I need return only rows which are different as in first table
I need select all data where Prod_No equals to baracode and Descript not equals to productname and Retail_PRC also not equals to pricesell.
I am not getting results with this code
List<DataRow> matchingRows = dtCatalogFromMySql.AsEnumerable()
.Where(a => dtDataForExistingProducts.AsEnumerable()
.Select(b => b.Field<string>("Prod_No"))
.Contains(a.Field<string>("barcode")))
.Where(a => !dtDataForExistingProducts.AsEnumerable()
.Select(b => b.Field<string>("Descript"))
.Equals(a.Field<string>("productname")))
.Where(a => !dtDataForExistingProducts.AsEnumerable()
.Select(b => b.Field<decimal>("Retail_PRC"))
.Equals(Convert.ToDecimal(a.Field<double>("pricesell"))))
.ToList();
I suppose, Contains() will also fetch the data if barcode = 123456 and Prod_No = 1234, it is right? If I am right what is right way to compare string exactly same

You may want to consider a clearer syntax such as:
var results = from t1 in dtCatalogFromMySql.AsEnumerable()
join t2 in dtDataForExistingProducts.AsEnumerable() on
(string)t1["barcode"] equals (string)t2["Prod_No"]
where (string)t1["productname"] != (string)t2["descript"] &&
Convert.ToDecimal((double)t1["pricesell"]) !=
(decimal)t2["Retail_PRC"]
select t2;
The Join is definitely the way to go. You can modify the select according to your required result set.
trighati makes a good point about using OR instead of AND. This is assuming that you want all of the data where at least one of your values changed where Prod_no and barcode are equal. This would change the query to be:
var results = from t1 in dtCatalogFromMySql.AsEnumerable()
join t2 in dtDataForExistingProducts.AsEnumerable() on
(string)t1["barcode"] equals (string)t2["Prod_No"]
where (string)t1["productname"] != (string)t2["descript"] ||
Convert.ToDecimal((double)t1["pricesell"]) !=
(decimal)t2["Retail_PRC"]
select t2;

Use Join to combine them into one result set, then filter the result set:
var combined = dtDataForExistingProducts.AsEnumerable()
.Join(dtCatalogFromMySql.AsEnumerable(),
ep => ep.Field<string>("Prod_No")
ce => ce.Field<string>("barcode"),
(ep, ce) => new {ExistingProduct = ep, CatalogEntry = ce})
.Where(m => !m.ExistingProduct.Field("Descript")
.Equals(m.CatalogEntry.Field("productname")))
.Where(m => decimal.Parse(m.ExistingProduct.Field("Retail_PRC").ToString())
!= decimal.Parse(m.CatalogEntry.Field("pricesell").ToString()))
.ToList()
;

How to sort a List<String> using data from a column in a ListView

In my application, there is a ListView that contains the Location name and the Picking Priority (Lowest is chosen first) of all the locations that products are kept in. As well as this, I am also creating temporary List's that contain only the locations an individual product is stored in. For example:-
LISTVIEW List<String>
-------- ------------
__________________________ __________________________
|Location |Picking Priority| | Location |
|---------|----------------| |--------------------------|
| A | 100 | | A |
| B | 50 | | C |
| C | 500 | | D |
| D | 150 | |__________________________|
|_________|________________|
What I want to happen is the List to be ordered based on the Picking Priority of that location in the ListView, lowest to highest.
In effect, this would mean the List above would now look like this:-
__________________________
| Location |
|--------------------------|
| A |
| D |
| C |
|__________________________|
How would this be possible to do?

You can order the items based on the listitems, it's ugly, it's slow (slower than using a class with both properties) but it can work.
I assume ListViewItem.Text contains the name of the location and ListViewItem.Subitems[1].Text is the column with the priority (in integer format):
var items = theListView.Items.Cast<ListViewItem>();
var sortedList = theStringList.OrderBy(d => items.Where(i => i.Text == d).Select(i => int.Parse(i.Subitems[1].Text)).First()).ToList();

LINQ grouping by nullable child and parent

everyone!
I've just faced a problem with timing out in my LINQ query.
I have 3 tables: Work, Projects and Subprojects.
Projects:
+--------+
| Id |<--+<--+
| Name | | |
+--------+ | |
SubProjects: | |
+--------+ | |
+->| Id | | |
| | Name | | |
| | ProjId |---+ |
| +--------+ |
| Work: |
| +------------+ |
| | Id | |
| | Type | |
| | ProjId |---+
+--| SubProjId | (nullable)
+------------+
I need to create a report based on Subprojects:
Group by subproject Id,
if subproject Id is null -> group by project Id
I've solved it by making two queries and then merging them, but when sometimes it times out.
I was doing it with
result1.AddRange(result2);
because
var temp = result1.Concat(result2);
is throwing an Exception:
Internal .NET Framework Data Provider error 1004, 0, Unresolvable Var used in Command: VarType=Computed, Id=2090.
Can somebody help me with creating it in one query?

I'm not sure what your code looks like so this might not be perfect but you could try something like this:
var result = from work in works
group work by work.SubProjId ?? work.ProjId into groupedWorks
select groupedWorks.ToList();
or
var result = works.GroupBy(work => work.SubProjId ?? work.ProjId).ToList();

try this query
var itemlist =contex.Work.where(x=>x.SubProjId !=null).Groupby(x=>x.SubProjId).Concat(Contex.Work.where(x=>x.SubProjId ==null).Groupby(x=>x.ProjId)).ToList();

I'm guessing this is what you need:
var groups = from work in ctx.Works // the work table
group work // we want to group whole work "rows"
// we are grouping by project id and subproject id
by new { ProjId = work.ProjId, SubProjId = work.SubProjId }
into g // and we are calling the grouping 'g'
select g; // select the group
// example of doing something with the groupings
foreach (var group in groups)
{
var key = group.Key; // gets a { ProjId, SubProjId } tuple
foreach (var work in group)
{
// each work is a row in the Work-table
}
}

group by dates and make mathematics on it using linq

I have datatable looks like this:
| date | value |
| 1/1/2013 10:28 | 5 |
| 1/1/2013 10:29 | 6 |
| 2/1/2013 01:54 | 6.5 |
| 2/1/2013 02:24 | 6.7 |
| 2/1/2013 03:14 | 8 |
I want to group the table into days.
then to calculate the avarage value of every group.
then to make avarage of all the values I calculated in step 2.
is there any good way to do it through linq ?
Thanks

of course you can use linq for this purpose:
var results = from p in list
group p by p.date.Date into g
select new { date = g.Key, value = g.Average(p=> p.value) };
var endAverage = results.Average(x => x.value);

MVC3 query clause custom query

First Table
+--------+------------+-------+
| type | variety | price |
+--------+------------+-------+
| apple | gala | 2.79 |
| apple | fuji | 0.24 |
| apple | limbertwig | 2.87 |
| orange | valencia | 3.59 |
| orange | navel | 9.36 |
| pear | bradford | 6.05 |
| pear | bartlett | 2.14 |
| cherry | bing | 2.55 |
| cherry | chelan | 6.33 |
+--------+------------+-------+
Second Table
+--------+----------+
| type | minprice |
+--------+----------+
| apple | 0.24 |
| cherry | 2.55 |
| orange | 3.59 |
| pear | 2.14 |
+--------+----------+
select type, min(price) as minprice
from fruits
group by type;
The first table is and example of the data that I have and the second table is what I want to get from the first.
I am using GenericRepository/UnitOfwork to get the data from repository.
repository.fruitRepository.Get().GroupBy(m => m.type);
But I can only get the type field but I want to get more fields.
Do I need to use a select clause before groupby? If yes, how can I select more fields?

The GroupBy method returns more data, but it's returned as an enumerable... you may be able to pull what you want out of it with a Select after the GroupBy...
repository.fruitRepository.Get()
.GroupBy(m => m.type)
.Select(m => new { type = m.Key, minPrice = m.Min(f => f.Price) });
Or if you prefer a LINQ statement:
var result = from x in repository.fruitRepository.Get()
group x by x.type into typeGroup
select new
{
type = typeGroup.Key,
minPrice = typeGroup.Min(item => item.Price)
};