I have a Linq Query made into a list called "ticket query"
I want to search ticket query for all the records that have specific data
I tried using FindAll() but it gives me an error
Argument matching parameter 'match' cannot convert from
'VB$AnonymousDelegate_1(Of JobPartForm,Nullable(Of Boolean))' to
'Predicate(Of JobPartForm)'.
I can't do the findall directly in the query because its being called at a separate time
is there another way to accomplish this, or am I using find all wrong?
ticketquery = (From ticket In dbContext.JobPartForm
Select ticket).ToList()
Dim formticket = ticketquery.FindAll(Function(f As JobPartForm) f.JobNum = ticketnum And f.FormNumber = formnum)
You can do the same using IQueryable<TSource>.Where method:
Dim formticket=dbContext.JobPartForm.Where((Function(f As JobPartForm) f.JobNum = ticketnum And f.FormNumber = formnum)).ToList();
The first thing is try to never call ToList extension method from a DbSet, that will load your entire table to memory, is really inefficient and more when you can filter your data on the server side.
Related
I have an API I am pinging which queries a cosmos db to return records.
I can filter on a simple string in my api call like so:
// return objects where '_Subject' field equals "filterTest"
string getUrl = $"...baseApiPath/?$filter=_Subject+eq+'filterTest'";
This is working perfectly.
But I cannot figure out the filter syntax to make my API query be based on ARRAY_CONTAINS.
// return objects where '_Attachments' field CONTAINS "945afd138aasdf545a2d1";
How would I do that? Is there a general reference for API filter syntax somewhere?
If you're asking about how to query, a query against a property with an array of values looks like this:
SELECT * FROM c WHERE ARRAY_CONTAINS(c._Attachments, "945afd138aasdf545a2d1")
Another example in this answer.
I am trying to learn a bit about ling. in the code below, I'm trying to retrieve records that have an activeuntil date which after the current date.
Dim context As DynamicsCRMEntities = New DynamicsCRMEntities()
Dim CustomerNoticeQuery = From NewsArticles In context.BusinessUnitNewsArticles Where NewsArticles.NewsArticle Like "customer" Select NewsArticles.ArticleTitle, NewsArticles.NewsArticle, NewsArticles.ActiveUntil
For Each result In CustomerNoticeQuery
If Date.Now.Date >= result.ActiveUntil Then
CustomerNotice.Text = result.NewsArticle.ToString
End If
Next
I keep running into this error but cannot get my head around it
System.NotSupportedException: 'LINQ to Entities does not recognize the method 'Boolean LikeString(System.String, System.String, Microsoft.VisualBasic.CompareMethod)' method, and this method cannot be translated into a store expression.'
The Like operator you are using there is VB-specific and, as the error message says, is not supported by EF. You need to use standard .NET functionality that the LINQ to Entities provider understands. If you want to do a partial match on Strings, that means using String.Contains:
Dim CustomerNoticeQuery = From NewsArticles In context.BusinessUnitNewsArticles
Where NewsArticles.NewsArticle.Contains("customer")
Select NewsArticles.ArticleTitle, NewsArticles.NewsArticle, NewsArticles.ActiveUntil
You really ought to break your LINQ queries over multiple lines like that too, for the sake of readability.
Note that that addresses your actual issue, which has nothing to do with dates, so the date part to the question was completely irrelevant. That said, why would you do a query with a Where clause and then use a loop to filter the results of that query? Why would you not include the additional filter in the Where clause? I'd also consider using a better subject variable name in the query:
Dim today = Date.Today
Dim CustomerNoticeQuery = From article In context.BusinessUnitNewsArticles
Where article.NewsArticle.Contains("customer")
And article.ActiveUntil < today
Select article.ArticleTitle, article.NewsArticle, article.ActiveUntil
I'm using npgsql as a nuget package in visual studio 2017 with visual basic.
Various commands do work very well but an ExecuteScalar allways returns 'nothing' although it should give a result.
The command looks like this:
Dim ser As Integer
Dim find = New NpgsqlCommand("SELECT serial from dbo.foreigncode WHERE code = '#code';", conn)
Dim fcode = New NpgsqlParameter("code", NpgsqlTypes.NpgsqlDbType.Varchar)
find.Parameters.Add(fcode)
find.Prepare()
fcode.Value = "XYZ"
ser = find.ExecuteScalar() ==> nothing
When the command string is copied as a value during debugging and pasted into the query tool of PGADMIN it delivers the correct result. The row is definitely there.
Different Commands executed with ExecuteNonQuery() work well, including ones performing UPDATE statements on the row in question.
When I look into the properties of the parameter fcode immediately before the ExecuteScalar it shows 'fcode.DataTypeName' caused an exception 'System.NotImplementedException'.
If I change my prepared statement to "SELECT #code" and set the value of the parameter to an arbitrary value just this value is returned. There is no access to the table taking place because the table name is not part of the SELECT in this case. If I remove the WHERE CLAUSE in the SELECT and just select one column, I would also expect that something has to be returned. But again it is nothing.
Yes there is a column named serial. It is of type bigint and can not contain NULL.
A Query shows that there is no single row that contains NULL in any column.
Latest findings:
I queried a different table where the search column and the result column happen to have the same datatype. It works, so syntax, passing of parameter, prepare etc. seems to work in principal.
The System.NotImplementedException in the DataTypeName property of the parameter occurs as well but it works anyway.
I rebuilt the index of the table in question. No change.
Still: when I copy/paste the CommandText and execute it in PGAdmin it shows the correct result.
Modifying the Command and using plain text there without parameter and without prepare still does yield nothing. The plain text CommandText was copy/pasted from PGAdmin where it was successfully executed before.
Very strange.
Reverting search column and result column also gives nothing as a result.
Please try these two alternatives and post back your results:
' Alternative 1: fetch the entire row, see what's returned
Dim dr = find.ExecuteReader()
While (dr.Read())
Console.Write("{0}\t{1} \n", dr[0], dr[1])
End While
' Alternative 2: Check if "ExecuteScalar()" returns something other than an int
Dim result = find.ExecuteScalar()
... and (I just noticed Honeyboy Wilson's response!) ...
Fix your syntax:
' Try this first: remove the single quotes around "#code"!
Dim find = New NpgsqlCommand("SELECT serial from dbo.foreigncode WHERE code = #code;", conn)
Update 1
Please try this:
Dim find = New NpgsqlCommand("SELECT * from dbo.foreigncode;", conn)
Q: Does this return anything?
Dim dr = find.ExecuteReader()
While (dr.Read())
Console.Write("{0}\t{1} \n", dr[0], dr[1])
End While
Q: Does this?
Dim result = find.ExecuteScalar()
Q: Do you happen to have a column named "serial"? What is it's data type? Is it non-null for the row(s) with 'XYZ'?
Please update your original post with this information.
Update 2
You seem to be doing ":everything right":
You've confirmed that you can connect,
You've confirmed that non-query updates to the same table work (with npgsql),
You've confirmed that the SQL queries themselves are valid (by copying/pasting the same SQL into PGAdmin and getting valid results).
As Shay Rojansky said, "System.NotImplementedException in the DataTypeName property" is a known issue stepping through the debugger. It has nothing to do with your problem: https://github.com/npgsql/npgsql/issues/2520
SUGGESTIONS (I'm grasping at straws)::
Double-check "permissions" on your database and your table.
Consider installing a different version of npgsql.
Be sure your code is detecting any/all error returns and exceptions (it sounds like you're probably already doing this, but it never hurts to ask)
... and ...
Enable verbose logging, both client- and server-side:
https://www.npgsql.org/doc/logging.html
https://www.postgresql.org/docs/9.0/runtime-config-logging.html
... Finally ...
Q: Can you make ANY query, from ANY table, using ANY query method (ExecuteReader(), ExecuteScalar(), ... ANYTHING) from your npgsql/.Net client AT ALL?
I finally found it. It's often the small things that can have a big impact.
When the value was assigned to the parameter a substring index was incorect.
Now it works perfectly.
Thanks to everybody who spent his time on this.
I am working with Unidata, and ADO.NET using the U2 .NET Provider. This may be a shot in the dark as there are not many resources for Unidata and .NET these days.
Currently I can only return a single MV record 153926þIþ and parse it using MV_To_DataTable. I'd like to return multiple records like 153926þIþÿ153926þIþÿ. Is there any built in mechanism for doing this? I fear I will have to write the extension to best accomodate me.
I retrieve a single record in a unidata subroutine this way:
SUBROUTINE GETITEMS(results)
EXECUTESQL "SELECT ID, STATUS, DESC FROM ITEMS TO GETITEM_LIST;"
DONE = 0
RECCNT = 0
LOOP
RECCNT += 1
READNEXTTUPLE REC FROM "GETITEM_LIST" ELSE DONE = 1
results := REC
IF RECCNT EQ 1 THEN EXIT
UNTIL DONE
REPEAT
results
CLEARSQL
RETURN
Simple subroutine that returns one record without any record marks. This works when I use the U2Parameter method called MV_To_DataTable to parse it into an existing datatable.
However when I change the subroutine line:
results:= REC to results:= REC : #RM to append the record marks and remove the limit of 1, the MV_To_DataTable no longer is able to parse it correctly. In fact it will throw System.IndexOutOfRangeException: Cannot find column 3.
VB.NET Code:
' ... Open database connection called U2Connection ...
Dim cmd = U2Connection.CreateCommand
cmd.CommandText = "CALL GETITEMS(?)"
cmd.CommandType = CommandType.StoredProcedure
cmd.Parameters.Clear()
cmd.Parameters.Add(New U2Parameter("#arg1", "") With {.Direction = ParameterDirection.InputOutput})
cmd.ExecuteNonQuery()
Dim tb As New DataTable
tb.Columns.Add("ID")
tb.Columns.Add("STATUS")
tb.Columns.Add("DESC")
cmd.Parameters.Item(0).MV_To_DataTable(tb) ' Error happens here
' System.IndexOutOfRangeException: Cannot find column 3.
It appears the method does not separate records. I could be interpretting this incorrectly.
*****UPDATE 2/9/2019
I went ahead and wrote my own extension method to support my return format with the record markers. It populates a datatable with records allowing me to continue as I normally would.
You are kind of straddling the Multivalue/System.Data divide here. If you have not already done so, I would suggest looking into the U2 Toolkit for .NET, which I believe is generally readily available if you are current on maintenance. It comes with some samples of how to do things like this in C# and VB as well some Entity Framework stuff.
But as to what is going on here, You are trying to put a U2Type.DynArray into a System.DataTable is kind of tricky as the DynArray is a Record state, which could contain multiple rows from multiple tables within a DataSet. As #RM is the terminator for a record so it turns DynArray into DynArray[] and you can't have that as a parameter as such.
To fix this with the minimum refactoring, you can still use MV_To_DataTable, but note that it is expecting your data to be tabular and in in a single record. These example assume a newline is an Attribute mark (#FM/#AM)
Here is the contents of what you are returning
Row1Column1
Row1Column2
Row1Column3:#RM
Row2Column1
Row2Column2
Row2Column3:#RM
Row13olumn1
Row13olumn2
Row13olumn3:#RM
And here is what MV_To_DataTable expects
Row1Column1:#VM:Row1Column2:#VM:Row1Column3
Row2Column1:#VM:Row2Column2:#VM:Row2Column3
Row3Column1:#VM:Row3Column2:#VM:Row3Column3
If you adjust your U2 sub to output that, it should work.
Additionally, you could try using your SQL command directly for .net, but that becomes perilous for other reasons depending on your data.
Good Luck!
Processing an XML file with LINQ to add records into a table in a SQL Server database via a data context. As we are adding records we need to assign the parents in various other tables. Most of the time we can find the existing parent and use it but sometimes we will need to create a new parent.
Thought we could do this like this:
Dim defaultPub As publication
defaultPub = New publication With {.name = e..Value}
Dim pub = _Data.publications.Where(Function(s) s.name = e..Value).DefaultIfEmpty(defaultPub).SingleOrDefault
.publication = pub
So we are trying to find a publication that matches e..Value from our XML, but if we can't find one then we use 'defaultPub'. If it does exist though we don't want to add it again. So maybe this approach is flawed anyway even if it did work...
Anyway it's not currently working, we get this error:
Unsupported overload used for query operator 'DefaultIfEmpty'.
The overload requires a publication and is getting one (I've checked the TypeNames in quickwatch), don't know what is going on here.
What we are really looking for is something like the find_or_create from activerecord for Ruby that LINQ seems to be a copied from.
Thanks in advance,
Dave.
OK, I can just do it like this:
Dim pub = _Data.publications.Where(Function(s) s.name = e.<source>.Value).SingleOrDefault
Dim newPub As publication
If Not IsNothing(pub) AndAlso pub.name <> "" Then
.publication = pub
Else
newPub = New publication With {.name = e.<source>.Value}
.publication = newPub
End If
Thanks Val!