I am new to c# and sql database. I got a problem when I request data using LINQ from my local database.
my code is like this:
CorporateActionEventType myEventType = (from en in m_db.m_EventTypes
where en.CorporateActionEventType1 == myCorporateActionEvent.EventType
select en).FirstOrDefault();
CAMAIL_PaymentOptions_vw myPaymentOptions = (from po in m_db.m_PaymentOptions
where po.EventID == myCorporateActionEvent.EventID
select po).FirstOrDefault();
CorporateActionEventType, CAMAIL_PaymentOptions_vw is a class I defined to request data from data base. This is LINQ code. I am really not familiar with that.
ArgumentNullException unhandled error occurred.
From a glance it looks like you may not be instantiating CorporateActionEventType correctly, try using "new".
It may help to post the error message or tell us where exactly you are getting the null exception.
Related
I have this linq query which works perfectly fine but sometimes it throws exception, following is start :
query = table.Include(x=>x.table2)
after applying few conditions in code finally following is the line which throws exception :
var data = await query.Skip(offset).Take(filter.PagingOption.PageSize).AsNoTracking().ToListAsync();
ErrorDetail :
System.Data.SqlClient.SqlException (0x80131904): The column 'Id' was specified multiple times for 't'.\r\n
Mostly it is observed that when IIS is restarted error occurs, but once the error is occurred on refresh this works totally fine. Which I guess is random behavior.
Any ideas ?
I'm using C# Npgsql and am trying to export data from Postgres using the COPY command. The below query will return 100+ rows. I would like to read the results out using a while loop just like you would do with NpgsqlDataReader.
The documentation on http://www.npgsql.org/doc/copy.html keeps throwing errors when I try to get a second row of results (second StartRow()).
Notes: Running second StartRow() returns following error message below:
An unhandled exception of type 'Npgsql.NpgsqlException' occurred in mscorlib.dll
Additional information: Unknown message code: 0
using (NpgsqlBinaryExporter reader = conn.BeginBinaryExport("COPY tableName(colONE, colTWO) TO STDOUT (FORMAT BINARY)"))
{
reader.StartRow();
Console.WriteLine(reader.Read<string>());
Console.WriteLine(reader.Read<int>(NpgsqlDbType.Smallint));
reader.StartRow(); //### <== ERROR HERE ###
Console.WriteLine(reader.Read<string>());
Console.WriteLine(reader.Read<int>(NpgsqlDbType.Smallint));
}
How do I read out ALL the rows in a WHILE loop or output in one shot?
If I understand the question correctly something like this might help:
using (NpgsqlBinaryExporter reader = conn.BeginBinaryExport("COPY tableName(colONE, colTWO) TO STDOUT (FORMAT BINARY)"))
{
while(reader.StartRow() > 0)
{
Console.WriteLine(reader.Read<string>());
Console.WriteLine(reader.Read<int>(NpgsqlDbType.Smallint));
}
}
This should read all the data from the table, and it solved my similar issue. I am still looking at ways of improving the performance, so let me know if you have any ideas.
I have an asp.net project in which, I would like to query DBPedia.
Using the following code I am getting an error:
public string testEndpoint()
{
//TEST02
SparqlRemoteEndpoint endpoint = new SparqlRemoteEndpoint(new Uri("http://dbpedia.org/sparql"), "http://dbpedia.org");
string res = "";
//Make a SELECT query against the Endpoint
SparqlResultSet results = endpoint.QueryWithResultSet("SELECT ?year WHERE {dbpedia:Rihanna dbpedia-owl:birthYear ?year}");
foreach (SparqlResult result in results)
{
res = result.ToString();
Console.WriteLine(result.ToString());}
Error message: "An exception of type 'System.Xml.XmlException' occurred in dotNetRDF.dll but was not handled in user code".
Even if I handle the exception the method cannot be executed. Regarding the details it says that there is an invalid XML-version 1.1.
As the XML comes from DBPedia I don't know how to change the xml version or how else I can handle this problem.
Virtuoso, which is the triple store used behind the dbpedia SPARQL endpoint, has updated its XML result generation. They replaced the XML version 1.0 with 1.1 in this commit. This causes the exception in the dotNetRDF parser.
Later on Virtuoso reverted the changes in the XML header. Hopefully DBPedia will update their binaries soon, so the old XML header appears again in the SPARQL results.
Source: http://github.com/openlink/virtuoso-opensource/issues/405
Update: I downloaded Ramone project, added it to my project and then ran the application again with debugger. The error is shown below:
public MediaTypeWriterRegistration GetWriter(Type t, MediaType mediaType)
{
...
CodecEntry entry = SelectWriters(t, mediaType).FirstOrDefault(); => this line throws error
...
}
Error occurs in CodecManager.cs. I am trying to figure out why it does not recognize json-patch media type. Could it be because writer is not being registered correctly? I am looking into it. If you figure out the problem, please let me know. Since you are the author of the library, it will be easier for you to figure out the issue. I will have to go through all the code files and methods to find the issue. Thanks!
I was excited to know that Ramone library supports json-patch operations but when I tried it, I got following error:
415- Unsupported Media Type
This is the same error that I get when I use RestSharp. I thought may be RestSharp does not support json-patch and errors out so I decided to try Ramone lib but I still get same error. Endpoint has no issues because when I try same command using Postman, it works but when I try it programmatically in C#, it throws unsupported media type error. Here is my code:
var authenticator = new TokenProvider("gfdsfdsfdsafdsafsadfsdrj5o97jgvegh", "sadfdsafdsafdsfgfdhgfhehrerhgJ");
JsonPatchDocument patch = new JsonPatchDocument<MetaData>();
patch.Add("/Resident2", "Boyle");
//patch.Replace("/Resident", "Boyle");
RSession = RamoneConfiguration.NewSession(new Uri("https://api.box.com"));
RSession.DefaultRequestMediaType = MediaType.ApplicationJson;
RSession.DefaultResponseMediaType = MediaType.ApplicationJson;
Ramone.Request ramonerequest = RSession.Bind("/2.0/files/323433290812/metadata");
ramonerequest.Header("Authorization", "Bearer " + authenticator.GetAccessToken(code).AccessToken);
//var ramoneresponse = ramonerequest.Patch(patch); //results in error: 405 - Method Not Allowed
var ramoneresponse = ramonerequest.Put(patch); //results in error: 415 - Unsupported Media Type
var responsebody = ramoneresponse.Body
Endpoint information is available here: http://developers.box.com/metadata-api
I used json-patch section in the following article as a reference:
http://elfisk.dk/Ramone/Documentation/Ramone.pdf
By the way I tried Patch() method (as shown in above ref. article) but that resulted in "Method not allowed" so I used Put() method which seems to work but then errors out because of json-patch operation.
Any help, guidance, tips in resolving this problem will be highly appreciated. Thanks much in advance.
-Sham
The Box documentation says you should use PUT (which is quite a bit funny). The server even tells you that it doesn't support the HTTP PATCH method (405 Method Not Allowed) - so PUT it must be.
Now, you tell Ramone to use JSON all the time (RSession.DefaultRequestMediaType = MediaType.ApplicationJson), so you end up PUT'ing a JSON document to Box - where you should be PUT'ing a JSON-Patch document.
Drop the "RSession.DefaultRequestMediaType = MediaType.ApplicationJson" statement and send the patch document as JSON-Patch with the use of: ramonerequest.ContentType("application/json-patch+json").Put(...).
I have a OdbcDataReader that gets data from a database and returns a set of records.
The code that executes the query looks as follows:
OdbcDataReader reader = command.ExecuteReader();
while (reader.Read())
{
yield return reader.AsMovexProduct();
}
The method returns an IEnumerable of a custom type (MovexProduct). The convertion from an IDataRecord to my custom type MovexProduct happens in an extension-method that looks like this (abbrev.):
public static MovexProduct AsMovexProduct(this IDataRecord record)
{
var movexProduct = new MovexProduct
{
ItemNumber = record.GetString(0).Trim(),
Name = record.GetString(1).Trim(),
Category = record.GetString(2).Trim(),
ItemType = record.GetString(3).Trim()
};
if (!record.IsDBNull(4))
movexProduct.Status1 = int.Parse(record.GetString(4).Trim());
// Additional properties with IsDBNull checks follow here.
return movexProduct;
}
As soon as I hit the if (!record.IsDBNull(4)) I get an OverflowException with the exception message "Arithmetic operation resulted in an overflow."
StackTrace:
System.OverflowException was unhandled by user code
Message=Arithmetic operation resulted in an overflow.
Source=System.Data
StackTrace:
at System.Data.Odbc.OdbcDataReader.GetSqlType(Int32 i)
at System.Data.Odbc.OdbcDataReader.GetValue(Int32 i)
at System.Data.Odbc.OdbcDataReader.IsDBNull(Int32 i)
at JulaAil.DataService.Movex.Data.ExtensionMethods.AsMovexProduct(IDataRecord record) [...]
I've never encountered this problem before and I cannot figure out why I get it. I have verified that the record exists and that it contains data and that the indexes I provide are correct. I should also mention that I get the same exception if I change the if-statemnt to this: if (record.GetString(4) != null). What does work is encapsulating the property-assignment in a try {} catch (NullReferenceException) {} block - but that can lead to performance-loss (can it not?).
I am running the x64 version of Visual Studio and I'm using a 64-bit odbc driver.
Has anyone else come across this? Any suggestions as to how I could solve / get around this issue?
Many thanks!
For any one experiencing the same issue, the way I solved this was to switch from the Odbc* classes to their OleDb* counterparts. This of course demands that your data driver has support for OleDb connections.
Which DB are you trying to talk to? If it uses some "private" column types that can cause problems. That doesn't apply to SQL Server of course :-)
Also check that you are compiling and running as x64 (Process Explorer will show you thsi and even plain tack manager shows it). devenv.exe will still be x86 but your actual binary should run as x64. The reason I mention is that crossing 32/64 bit boundary is notorious for breaking 3rd party ODBC drivers.