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Mongodb.Bson BsonBinaryWriter can't write field with name

I'm trying to write int value to BsonBinaryWriter using WriteInt32, but receive exception "WriteName can only be called when State is Name, not when State is Initial".
code sample
using MongoDB.Bson;
using MongoDB.Bson.IO;
BsonBinaryWriter writer = new BsonBinaryWriter(new MemoryStream());
writer.WriteInt32("t", 1); // receive exception here

you should call WriteStartDocument first since what you're doing is creating a BSON document. So you're trying to add t : 1 value, but given that BSON document should roughly speaking correspond to JSON rules, you should open a bracket { (via WriteStartDocument) and close it at the end of a document (via WriteEndDocument).
See:
using var memoryStream = new MemoryStream();
using var writer = new BsonBinaryWriter(memoryStream);
writer.WriteStartDocument();
writer.WriteInt32("t", 1); // receive exception here
writer.WriteEndDocument();
memoryStream.Position = 0;
using var reader = new BsonBinaryReader(memoryStream);
var context = BsonDeserializationContext.CreateRoot(reader);
var document = BsonDocumentSerializer.Instance.Deserialize(context);
Console.WriteLine(document.ToString()); // => { "t" : 1 }

Consecutive XML serialization causes - Token StartElement in state EndRootElement would result in an invalid XML document

I am writing to the file XML serialization of the object, generated by validator.MatchPossiblyValid(string input)method. First call, serializes and write to the file. However, the second call fails with an exception: System.InvalidOperationException: 'Token StartElement in state EndRootElement would result in an invalid XML document. Make sure that the ConformanceLevel setting is set to ConformanceLevel.Fragment or ConformanceLevel.Auto if you want to write an XML fragment. '
XmlSerializerNamespaces emptyNS = new XmlSerializerNamespaces(new[] { XmlQualifiedName.Empty });
var serializer = new XmlSerializer(typeof(PDPCustomerInfoInvalid));
var settings = new XmlWriterSettings();
settings.OmitXmlDeclaration = true;
//settings.Indent = true;
using (var stream = new System.IO.StreamWriter(args[1], true))
{
using (var writer = XmlWriter.Create(stream, settings))
{
serializer.Serialize(writer, validator.MatchPossiblyValid("STRING FOR PARSING"), emptyNS);
stream.Write(Environment.NewLine);
stream.Flush();
//Line below throws the exception
serializer.Serialize(writer, validator.MatchPossiblyValid("STRING FOR PARSING"), emptyNS);
stream.Write(Environment.NewLine);
stream.Flush();
}
}

You are trying to use a single XmlWriter to create an XML file with multiple root elements. However, the XML standard requires exactly one root element per XML document. Your XmlWriter is throwing the exception to indicate that the XML being created is invalid. (MCVE here.)
If you really need to concatenate two XML documents into a single file, you could use separate XmlWriters created with XmlWriterSettings.CloseOutput set to false:
using (var stream = new System.IO.StreamWriter(args[1], true))
{
var settings = new XmlWriterSettings();
settings.OmitXmlDeclaration = true;
//settings.Indent = true;
settings.CloseOutput = false;
using (var writer = XmlWriter.Create(stream, settings))
{
serializer.Serialize(writer, validator.MatchPossiblyValid("STRING FOR PARSING"), emptyNS);
}
stream.Write(Environment.NewLine);
stream.Flush();
using (var writer = XmlWriter.Create(stream, settings))
{
serializer.Serialize(writer, validator.MatchPossiblyValid("STRING FOR PARSING"), emptyNS);
}
//Line below throws the exception
stream.Write(Environment.NewLine);
stream.Flush();
}
Sample fiddle.
Or, better yet, don't do this at all, since an "XML Document" with multiple roots is, as stated above, not valid. Instead, serialize both objects inside some container element.

Avoid XML Escape Double Quote

I'm currently trying to serialize a class into XML to be posted to php web service.
Whenever I did the normal serialization using XMLSerializer, XML declaration is always appear in the first line of the XML document (similar as to <?xml ....?>). I tested the XML and unable to get it working because the endpoint does not accept XML declaration and I can't do anything about it.
I'm unfamiliar with XML Serialization in C# to be honest.
Therefore, I used XMLWriter to do this as below :-
private string SerializeClassToString(GetRiskReport value)
{
var emptyNS = new XmlSerializerNamespaces(new[] { XmlQualifiedName.Empty });
var ser = new XmlSerializer(value.GetType());
var settings = new XmlWriterSettings();
settings.OmitXmlDeclaration = true;
using (var stream = new StringWriter())
{
using (var writer = XmlWriter.Create(stream, settings))
{
ser.Serialize(writer, value, emptyNS);
return stream.ToString();
}
}
}
Result for the Namespace is
<GetRiskReport FCRA=\"false\" ReturnResultsOnly=\"false\" Monitoring=\"false\">
... and I'm able to omit the XML Declaration, however I'm being introduced with 2 new problem.
I got \r\n for new line and I have escaped double quote such as ReturnResultsOnly=\"false\" Monitoring=\"false\" which is also unable processed by the endpoint.
I would like to ask is that does anyone can give me an idea on how to change the XmlWriterSetting to omit XML Declaration, avoid \r\n and also avoid escaped double quotes \"
Thanks for your advice in advance.
Simon

Try with following settings
settings.NewLineHandling = NewLineHandling.None;
settings.CheckCharacters = false;

private void SerializeClassToString(GetRiskReport value)
{
var emptyNS = new XmlSerializerNamespaces(new[]{XmlQualifiedName.Empty});
var ser = new XmlSerializer(value.GetType());
var settings = new XmlWriterSettings();
settings.OmitXmlDeclaration = true;
string path = 'your_file_path_here'
if (File.Exists(path)) File.Delete(path);
FileStream stream = File.Create(path);
using (var writer = XmlWriter.Create(stream, settings))
{
ser.Serialize(writer, value, emptyNS);
return;
}
}
There was no way to avoid ms bug or thier intensional specification about xmlserializing.It's easier and faster to use filestream object.

Write to a File using CsvHelper in C#

I tried to write to CSV file using CsvHelper in C#.
This is the link to the library http://joshclose.github.io/CsvHelper/
I used the code in web site.
Here is my code:
var csv = new CsvWriter(writer);
csv.Configuration.Encoding = Encoding.UTF8;
foreach (var value in valuess)
{
csv.WriteRecord(value);
}
It writes only a part of data to csv file.
Last rows were missing.
Could you please help with this.

You need to flush the stream. The Using statement will flush when out of scope.
using (TextWriter writer = new StreamWriter(#"C:\test.csv", false, System.Text.Encoding.UTF8))
{
var csv = new CsvWriter(writer);
csv.WriteRecords(values); // where values implements IEnumerable
}

when, I added this code after the loop code is working well
var csv = new CsvWriter(writer);
csv.Configuration.Encoding = Encoding.UTF8;
foreach (var value in valuess)
{
csv.WriteRecord(value);
}
writer.Close();
The problem occurred because I did not close the Connection

Assuming that writer is some kind of TextWriter, you should add a call to flush the contents before closing the writer:
writer.Flush()
If the last lines are missing, this is the most likely reason.

Adding to #greg's answer:
using (var sr = new StreamWriter(#"C:\out.csv", false, Encoding.UTF8)) {
using (var csv = new CsvWriter(sr)) {
csv.WriteRecords(values);
}
}

streaming XML serialization in .net

I'm trying to serialize a very large IEnumerable<MyObject> using an XmlSerializer without keeping all the objects in memory.
The IEnumerable<MyObject> is actually lazy..
I'm looking for a streaming solution that will:
Take an object from the IEnumerable<MyObject>
Serialize it to the underlying stream using the standard serialization (I don't want to handcraft the XML here!)
Discard the in memory data and move to the next
I'm trying with this code:
using (var writer = new StreamWriter(filePath))
{
var xmlSerializer = new XmlSerializer(typeof(MyObject));
foreach (var myObject in myObjectsIEnumerable)
{
xmlSerializer.Serialize(writer, myObject);
}
}
but I'm getting multiple XML headers and I cannot specify a root tag <MyObjects> so my XML is invalid.
Any idea?
Thanks

The XmlWriter class is a fast streaming API for XML generation. It is rather low-level, MSDN has an article on instantiating a validating XmlWriter using XmlWriter.Create().
Edit: link fixed. Here is sample code from the article:
async Task TestWriter(Stream stream)
{
XmlWriterSettings settings = new XmlWriterSettings();
settings.Async = true;
using (XmlWriter writer = XmlWriter.Create(stream, settings)) {
await writer.WriteStartElementAsync("pf", "root", "http://ns");
await writer.WriteStartElementAsync(null, "sub", null);
await writer.WriteAttributeStringAsync(null, "att", null, "val");
await writer.WriteStringAsync("text");
await writer.WriteEndElementAsync();
await writer.WriteCommentAsync("cValue");
await writer.WriteCDataAsync("cdata value");
await writer.WriteEndElementAsync();
await writer.FlushAsync();
}
}

Here's what I use:
using System;
using System.Collections.Generic;
using System.Xml;
using System.Xml.Serialization;
using System.Text;
using System.IO;
namespace Utils
{
public class XMLSerializer
{
public static Byte[] StringToUTF8ByteArray(String xmlString)
{
return new UTF8Encoding().GetBytes(xmlString);
}
public static String SerializeToXML<T>(T objectToSerialize)
{
StringBuilder sb = new StringBuilder();
XmlWriterSettings settings =
new XmlWriterSettings {Encoding = Encoding.UTF8, Indent = true};
using (XmlWriter xmlWriter = XmlWriter.Create(sb, settings))
{
if (xmlWriter != null)
{
new XmlSerializer(typeof(T)).Serialize(xmlWriter, objectToSerialize);
}
}
return sb.ToString();
}
public static void DeserializeFromXML<T>(string xmlString, out T deserializedObject) where T : class
{
XmlSerializer xs = new XmlSerializer(typeof (T));
using (MemoryStream memoryStream = new MemoryStream(StringToUTF8ByteArray(xmlString)))
{
deserializedObject = xs.Deserialize(memoryStream) as T;
}
}
}
}
Then just call:
string xml = Utils.SerializeToXML(myObjectsIEnumerable);
I haven't tried it with, for example, an IEnumerable that fetches objects one at a time remotely, or any other weird use cases, but it works perfectly for List<T> and other collections that are in memory.
EDIT: Based on your comments in response to this, you could use XmlDocument.LoadXml to load the resulting XML string into an XmlDocument, save the first one to a file, and use that as your master XML file. For each item in the IEnumerable, use LoadXml again to create a new in-memory XmlDocument, grab the nodes you want, append them to the master document, and save it again, getting rid of the new one.
After you're finished, there may be a way to wrap all of the nodes in your root tag. You could also use XSL and XslCompiledTransform to write another XML file with the objects properly wrapped in the root tag.

You can do this by implementing the IXmlSerializable interface on the large class. The implementation of the WriteXml method can write the start tag, then simply loop over the IEnumerable<MyObject> and serialize each MyObject to the same XmlWriter, one at a time.
In this implementation, there won't be any in-memory data to get rid of (past what the garbage collector will collect).