I'm looking for a concise one line method to get a single value from a DataTable using lambda using VB.Net
This code works
OPT_UDLY = (From X In DATA.OPTIONs
Where X.CONTRACT = CTC
Select X.UDLY).Single()
but I'd like to get the value in one line like this (which doesn't work)
OPT_UDLY = DATA.Where(function(t) t.contract.Equals(CTC)).Distinct()
Any suggestions please?
Try this:
OPT_UDLY = Data.OPTIONs.Where(Function(t) t.CONTRACT = CTC).Select(Function(x) x.UDLY).Single()
Since you use Data.OPTIONs in the multiple LINQ lines, it should be consistently used for single line too.
Also, since you only need the UDLY element, use further Select LINQ expression in single line style, like what you did in your multiple lines.
And lastly, use Single to return the matching value if there is only one match, like what you already did.
Just remove the line feeds:
OPT_UDLY = (From X In DATA.OPTIONs Where X.CONTRACT = CTC Select X.UDLY).Single()
It's shorter and more readable than the lambda equivalent:
OPT_UDLY = Data.OPTIONs.Where(Function(t) t.CONTRACT = CTC).Select(Function(x) x.UDLY).Single()
Related
I'm working with a query that is used by multiple services but the number of results returned are different based on filtering.
To avoid copying and pasting the query, I was wondering if it was possible to pass in piece of sql into a sql parameter and it would work? I'm also open to alternative solutions.
EXAMPLE:
MapSqlParameterSource parameters = new MapSqlParameterSource();
parameters.addValue("filter", "and color = blue");
namedParameterJdbcTemplate.query(“select * from foo where name = 'Joe' :filter”, parameters, new urobjRowMapper());
It is very dangerous and fragile to let callers pass SQL to your program, because it opens you up to SQL injection - the very problem the parameters are there to prevent.
A better approach is to pre-code the filters in your query, and protect them by a special "selector" parameter:
SELECT *
FROM foo
WHERE name='Joe' AND
(
(:qselect = 1 AND color='blue')
OR (:qselect = 2 AND startYear = 2021)
OR (:qselect = 3 AND ...)
)
The data that appears does not match the conditions that have been applied
I implemented SQL code in the Navicat application, and have changed the structure of the code several times but it still doesn't work,
data that is not of ilart condition type
still appears
SELECT SERMAT,ILART,sum(GKSTP) as jumlah
FROM swift_zab_iw39
WHERE ILART='OVH' OR ILART='TST' and SERMAT='024147-000:09052'
GROUP BY ILART,SERMAT
Use IN operator:
WHERE ILART IN('OVH','TST') AND SERMAT = '024147-000:09052'
Add parenthesis to the OR condition in the WHERE clause as:
WHERE (ILART = 'OVH' OR ILART = 'TST') AND SERMAT = '024147-000:09052'
I have a list of Tuples I am trying to run a Select and Where query on to return a list of Objects from the Tuple.Item5 parameter. In my where clause I am looking to match Tuple.Item4 to a local variable.
I'm not sure what the VB.NET syntax is for the Select portion, I only know the c# syntax.
Essentially I am trying to select Tuple.Item5 from my list of tuples where Tuple.Item4 = sCurID. I'm unsure as to what should go in the Select section although in c# I believe it would be Select(t => t.Item5)
This is what I have:
listObj = listTuples.Select( Unsure What Goes Here ).Where(Function(w) w.Item4 = sCurID)
Once you apply the Select in C# or VB, you have reduced the Tuple to the Item5 value and can't access Item4. Do the Select last:
Dim listObj = listTuples.Where(Function(t) t.Item4 = sCurId).Select(Function(t) t.Item5)
listObj = listTuples.Select(Function(t) t.Item5).Where(Function(w) w.Item4 = sCurID).ToList()
I am stuck with a problem here. I am trying to compare items in a list to another list with much more items using linq.
For example:
list 1: 10,15,20
list 2: 10,13,14,15,20,30,45,54,67,87
I should get TRUE if all the items in list 1 occur in list 2. So the example above should return TRUE
Like you can see I can't use sequenceEquals
Any ideas?
EDIT:
list2 is actually not a list it is a column in sql thas has following values:
<id>673</id><id>698</id><id>735</id><id>1118</id><id>1120</id><id>25353</id>.
in linq I did the following queries thanks to Jon Skeets help:
var query = from e in db
where e.taxonomy_parent_id == 722
select e.taxonomy_item_id;
query is IQueryable of longs at this moment
var query2 = from e in db
where query.Contains(e.taxonomy_item_id)
where !lsTaxIDstring.Except(e.taxonomy_ids.Replace("<id>", "")
.Replace("</id>", "")
.Split(',').ToList())
.Any()
select e.taxonomy_item_id;
But now I am getting the error Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains() operator.
How about:
if (!list1.Except(list2).Any())
That's about the simplest approach I can think of. You could explicitly create sets etc if you want:
HashSet<int> set2 = new HashSet<int>(list2);
if (!list1.Any(x => set2.Contains(x)))
but I'd expect that to pretty much be the implementation of Except anyway.
This should be what you want:
!list1.Except(list2).Any()
var result = list1.All(i => list2.Any(i2 => i2 == i));
Customer.text is a field in an T-SQL DB (that I do not control and thus may not alter) of type "text".
I'd like to do something like this:
List<string> compare = new List<string>();
compare.Add("one");
compare.Add("two");
var q = from t in customer
where t.text.Contains( compare.First())
select t;
this will work.
But now I'd like to do something like: (!NOT WORKING!)
var q = from t in customer
where compare.Contains( t.text )
select t;
How can I achieve this? Is it even possible?
EDIT: The problem is obviously not exactly clear: A text column in SQL cannot be queried using "=" but only with LIKE. Thus the compare.Contains( t.text ) will result in an error, as it is converted into a query using "=".
What I did not tell - I thought it is irrelevant - is, that I use LINQ-to-ORM (LLBLGen in this case).
What I tried instead:
var q = from t in customer
where compare.Any( x => t.text.Contains(x) )
select t;
Now this did not work also. Currently I'm not at work, but the exception was something with a ConstantExpression not being convertable into a SetExpression.
I hope this gave some clarification.
EDIT2:
Joseph pointed this out to me: PredicateBuilder. It creates an Expression on a given ObjectType.
Now my problem is, that my type is an anonymous type out of multiple joins.
Is there an easy or elegant way to handle this?
Now I might be missing something, but your code looks like it should work. Did you include the namespaces at the top of the file?
using System.Linq;
using System.Linq.Expressions;
You could also rewrite it without the Linq2Sql syntax, like:
var q = customer.Where(c => compare.Contains(c.text));
You could build your query using LinqKit's free predicate builder class. Here is a blog post which describes its use and has a link to the download site.
http://thecodeslinger.wordpress.com/2008/10/28/linqkit-predicatebuildert-goodness/
Below is a code sample from the post
//First get a list of keywords that match the description entered.
string[] parts = txtInclude.Text.Split(new[] {‘ ‘});
string[] noparts = null;
if(txtButNot.Text.Trim().Length > 0)
noparts = txtExclude.Text.Trim().Split(new[] {‘ ‘});
var pred = PredicateBuilder.True<Pet>();
//here is where you would loop through your compare object
parts.ForEach(p => pred = pred.And(pl => pl.description.Contains(p)));
if(noparts != null)
noparts.ForEach(p => pred = pred.And(pl => !pl.description.Contains(p)));
var pets = from s in db.Pets.Where(pred)
select s;
You have to convert the text field to string
var query = from t in dataContext.table
where compare.Contains(t.textField.ToString())
select t;