I am overriding a method which has an XmlReader being passed in, I need to find a specific element, add an attribute and then either create a new XmlReader or just replace the existing one with the modified content. I am using C#4.0
I have investigated using XElement (Linq) but I can't seem to manipulate an existing element and add an attribute and value.
I know that the XmlWriter has WriteAttributeString which would be fantastic but again I am not sure how it all fits together
I would like to be able to do something like --- This is pseudo-code!
public XmlReader DoSomethingWonderful(XmlReader reader)
{
Element element = reader.GetElement("Test");
element.SetAttribute("TestAttribute","This is a test");
reader.UpdateElement(element);
return reader;
}
XmlReader/Writer are sequential access streams. You will have to read in on one end, process the stream how you want, and write it out the other end. The advantage is that you don't need to read the whole thing into memory and build a DOM, which is what you'd get with any XmlDocument-based approach.
This method should get you started:
private static void PostProcess(Stream inStream, Stream outStream)
{
var settings = new XmlWriterSettings() { Indent = true, IndentChars = " " };
using (var reader = XmlReader.Create(inStream))
using (var writer = XmlWriter.Create(outStream, settings)) {
while (reader.Read()) {
switch (reader.NodeType) {
case XmlNodeType.Element:
writer.WriteStartElement(reader.Prefix, reader.Name, reader.NamespaceURI);
writer.WriteAttributes(reader, true);
//
// check if this is the node you want, inject attributes here.
//
if (reader.IsEmptyElement) {
writer.WriteEndElement();
}
break;
case XmlNodeType.Text:
writer.WriteString(reader.Value);
break;
case XmlNodeType.EndElement:
writer.WriteFullEndElement();
break;
case XmlNodeType.XmlDeclaration:
case XmlNodeType.ProcessingInstruction:
writer.WriteProcessingInstruction(reader.Name, reader.Value);
break;
case XmlNodeType.SignificantWhitespace:
writer.WriteWhitespace(reader.Value);
break;
}
}
}
}
This is not quite as clean as deriving your own XmlWriter, but I find that it's much easier.
[EDIT]
An example of how you would open two streams at once might be something like this:
using (FileStream readStream = new FileStream(#"c:\myFile.xml", FileMode.OpenOrCreate, FileAccess.Read, FileShare.Write)) {
using (FileStream writeStream = new FileStream(#"c:\myFile.xml", FileMode.OpenOrCreate, FileAccess.Write)) {
PostProcess(readStream, writeStream);
}
}
I fixed it using the following duct tape coding
public XmlReader FixUpReader(XmlReader reader)
{
reader.MoveToContent();
string xml = reader.ReadOuterXml();
string dslVersion = GetDSLVersion();
string Id = GetID();
string processedValue = string.Format("<ExampleElement dslVersion=\"{1}\" Id=\"{2}\" ", dslVersion, Id);
xml = xml.Replace("<ExampleElement ", processedValue);
MemoryStream ms = new MemoryStream(System.Text.Encoding.ASCII.GetBytes(xml));
XmlReaderSettings settings = new XmlReaderSettings();
XmlReader myReader = XmlReader.Create(ms);
myReader.MoveToContent();
return myReader;
}
I feel dirty for doing it this way but it is working....
You can't easily do this with XmlReader - at least, not without reading the whole XML document in from the reader, futzing with it and then creating a new XmlReader from the result. That defeats a lot of the point of using XmlReader though - namely the ability to stream large documents.
You could potentially derive from XmlReader, forwarding most method calls to the existing reader but intercepting them where appropriate to add extra attributes etc... but I suspect that code would be really quite complex and fragile.
I would rather prefer to load the xml into XmlDocument object and use Attributes collection to modify the value and call Save method to update this value. Below code works for me.
public static void WriteElementValue ( string sName, string element, string value)
{
try
{
var node = String.Format("//elements/element[#name='{0}']", sName);
var doc = new XmlDocument { PreserveWhitespace = true };
doc.Load(configurationFileName);
var nodeObject = doc.SelectSingleNode(node);
if (nodeObject == null)
throw new XmlException(String.Format("{0} path does not found any matching
node", node));
var elementObject = nodeObject[element];
if (elementObject != null)
{
elementObject.Attributes["value"].Value = value;
}
doc.Save(configurationFileName);
}
catch (Exception ex)
{
throw new ExitLevelException(ex, false);
}
}
I've also observed when you use XmlWriter or XmlSerializer the whitespaces were not correctly preserved, this could be annoying sometimes
string newvalue = "10";
string presentvalue = "";
string newstr = "";
XmlReader xmlr = XmlReader.Create(new StringReader(str));
while (xmlr.Read())
{
if (xmlr.NodeType == XmlNodeType.Element)
{
if (xmlr.Name == "priority")
{
presentvalue = xmlr.ReadElementContentAsString();
newstr = str.Replace(presentvalue, newvalue);
}
}
}
//newstr can be written back to file... that is the edited xml
Related
I needed to get the encoding type from the top of the xml file
<?xml version=“1.0” encoding=“utf-8”?>
but only the encoding="utf-8" is needed
the "utf-8" only without the quotation mark, how can I achieve this using streamreader?
You need utf-8 or encoding="utf-8" ? this block returns utf-8 as a result. If you need encoding="utf-8", you need to change.
using (var sr = new StreamReader(#"yourXmlFilePath"))
{
var settings = new XmlReaderSettings { ConformanceLevel = ConformanceLevel.Fragment };
using (var xmlReader = XmlReader.Create(sr, settings))
{
if (!xmlReader.Read()) throw new Exception("No line");
var result = xmlReader.GetAttribute("encoding"); //returns utf-8
}
}
Since it's xml, I would recommend XmlTextReader that provides fast, non-cached, forward-only access to XML data and read just top of the xml file since declaration is there. See following method:
string FindXmlEncoding(string path)
{
XmlTextReader reader = new XmlTextReader(path);
reader.Read();
if (reader.NodeType == XmlNodeType.XmlDeclaration)
{
while (reader.MoveToNextAttribute())
{
if (reader.Name == "encoding")
return reader.Value;
}
}
return null;
}
how can I achieve this using StreamReader?
Something like this:
using (StreamReader sr = new StreamReader("XmlFile.xml"))
{
string line = sr.ReadLine();
int closeQuoteIndex = line.LastIndexOf("\"") - 1;
int openingQuoteIndex = line.LastIndexOf("\"", closeQuoteIndex);
string encoding = line.Substring(openingQuoteIndex + 1, closeQuoteIndex - openingQuoteIndex);
}
const string ENCODING_TAG = "encoding"; //You are searching for this. Lets make it constant.
string line = streamReader.ReadLine(); //Use your reader here
int start = line.IndexOf(ENCODING_TAG);
start = line.IndexOf('"', start)+1; //Start of the value
int end = line.IndexOf('"', start); //End of the value
string encoding = line.Substring(start, end-start);
NOTE: This approach expects the encoding to be in the first line of an existing declaration. Which it does not need to be.
I am trying to retrieve all elements from an XML file, but I just can reach one, is there any way I can retrieve all?
HttpWebResponse objResponse = (HttpWebResponse)objRequest.GetResponse();
using (XmlReader reader = XmlReader.Create(new StreamReader(objResponse.GetResponseStream())))
{
while (reader.Read())
{
#region Get Credit Score
//if (reader.ReadToDescendant("results"))
if (reader.ReadToDescendant("ssnMatchIndicator"))
{
string ssnMatchIndicator = reader.Value;
}
if (reader.ReadToDescendant("fileHitIndicator"))
{
reader.Read();//this moves reader to next node which is text
result = reader.Value; //this might give value than
Res.Response = true;
Res.SocialSecurityScore = result.ToString();
//break;
}
else
{
Res.Response = false;
Res.SocialSecurityScore = "Your credit score might not be available. Please contact support";
}
#endregion
#region Get fileHitIndicator
if (reader.ReadToDescendant("fileHitIndicator"))
{
reader.Read();
Res.fileHitIndicator = reader.Value;
//break;
}
#endregion
}
}
Can somebody help me out with this issue?
I am also using objResponse.GetResponseStream() because the XML comes from a response from server.
Thanks a lot in advance.
Try this :
XmlDataDocument xmldoc = new XmlDataDocument();
XmlNodeList xmlnode ;
int i = 0;
string str = null;
FileStream fs = new FileStream("product.xml", FileMode.Open, FileAccess.Read);
xmldoc.Load(fs);
xmlnode = xmldoc.GetElementsByTagName("Product");
for (i = 0; i <= xmlnode.Count - 1; i++)
{
xmlnode[i].ChildNodes.Item(0).InnerText.Trim();
str = xmlnode[i].ChildNodes.Item(0).InnerText.Trim() + " " + xmlnode[i].ChildNodes.Item(1).InnerText.Trim() + " " + xmlnode[i].ChildNodes.Item(2).InnerText.Trim();
MessageBox.Show (str);
}
I don't know why what you're doing is not working, but I wouldn't use that method. I've found the following to work well. Whether you're getting the xml from a stream, just put it into a string and bang...
StreamReader reader = new StreamReader(sourcepath);
string xml = reader.ReadToEnd();
reader.Close();
XmlDocument doc = new XmlDocument();
doc.LoadXml(xml);
XmlNodeList list = doc.GetElementsByTagName("*");
foreach (XmlNode nd in list)
{
switch (nd.Name)
{
case "ContactID":
var ContactIdent = nd.InnerText;
break;
case "ContactName":
var ContactName = nd.InnerText;
break;
}
}
To capture what is between the Xml tags, if there are no child Xml tags, use the InnerText property, e.g. XmlNode.InnerText. To capture what is between the quotes in the nodes' attributes, use XmlAttribute.Value.
As for iterating through the attributes, if one of your nodes has attributes, such as the elements "Name", "SpectralType" and "Orbit" in the Xml here:
<System>
<Star Name="Epsilon Eridani" SpectralType="K2v">
<Planets>
<Planet Orbit="1">Bill</Planet>
<Planet Orbit="2">Moira</Planet>
</Planets>
</Star>
</System>
Detect them using the Attributes property, and iterate through them as shown:
if (nd.Attributes.Count > 0)
{
XmlAttributeCollection coll = nd.Attributes;
foreach (XmlAttribute cn in coll)
{
switch (cn.Name)
{
case "Name":
thisStar.Name = cn.Value;
break;
case "SpectralType":
thisStar.SpectralClass = cn.Value;
break;
}
}
}
You might find some more useful information HERE.
I am currently working with an xml file which usually should contain a list of custom objects (List), but from time to time can simply contain a string node with a message. I have a code which deserializes this file:
private T DeserializeFile<T>(string filePath)
{
StreamReader readFileStream = new StreamReader(#filePath);
var serializerObj = new XmlSerializer(typeof(T));
return (T)serializerObj.Deserialize(readFileStream);
}
This works for List but for simple string throws an error (InvalidOperationException - Root element is missing, or " was not expected."). How can I detect the case when the file contains only the string element and return null from the function?
Basically this is what I want to do:
private T DeserializeFile<T>(string filePath)
{
StreamReader readFileStream = new StreamReader(#filePath);
var serializerObj = new XmlSerializer(typeof(T));
try
{
return (T)serializerObj.Deserialize(readFileStream);
}
catch (Exception ex)
{
return null;
}
}
This should do what you're trying to do. It uses XDocument to load and parse the file, so that it can check if there are any elements before trying to deserialize it.
private T DeserializeFile<T>(string filePath)
{
var xdoc = XDocument.Load(filePath);
if (xdoc.Root.Elements().Any())
{
var serializerObj = new XmlSerializer(typeof(T));
return (T)serializerObj.Deserialize(xdoc.CreateReader());
}
else
return default(T);
}
This assumes that you always have valid XML files, with the only difference being whether the root contains more elements or just text, e.g. a list like
<someRoot>
<someObj>
</someObj>
<someObj>
</someObj>
</someRoot>
And a "string" like
<someRoot>just a string</someRoot>
I am looking on Internet how keep the carriage return from XML data but I could not find the answer, so I'm here :)
The objective is to write in a file the content of a XML data. So, if the value of the node contains some "\r\n" data, the soft need to write them in file in order to create new line, but it doesn't write, even with space:preserve.
Here is my test class:
XElement xRootNode = new XElement("DOCS");
XElement xData = null;
//XNamespace ns = XNamespace.Xml;
//XAttribute spacePreserve = new XAttribute(ns+"space", "preserve");
//xRootNode.Add(spacePreserve);
xData = new XElement("DOC");
xData.Add(new XAttribute("FILENAME", "c:\\titi\\prout.txt"));
xData.Add(new XAttribute("MODE", "APPEND"));
xData.Add("Hi my name is Baptiste\r\nI'm a lazy boy");
xRootNode.Add(xData);
bool result = Tools.writeToFile(xRootNode.ToString());
And here is my process class:
try
{
XElement xRootNode = XElement.Parse(xmlInputFiles);
String filename = xRootNode.Element(xNodeDoc).Attribute(xAttributeFilename).Value.ToString();
Boolean mode = false;
try
{
mode = xRootNode.Element(xNodeDoc).Attribute(xWriteMode).Value.ToString().ToUpper().Equals(xWriteModeAppend);
}
catch (Exception e)
{
mode = false;
}
String value = xRootNode.Element(xNodeDoc).Value;
StreamWriter destFile = new StreamWriter(filename, mode, System.Text.Encoding.Unicode);
destFile.Write(value);
destFile.Close();
return true;
}
catch (Exception e)
{
return false;
}
Does anybody have an idea?
If you want to preserve cr lf in element or attribute content when saving a XDocument or XElement you can do that by using certain XmlWriterSettings, namely NewLineHandling to Entitize:
string fileName = "XmlOuputTest1.xml";
string attValue = "Line1.\r\nLine2.";
string elementValue = "Line1.\r\nLine2.\r\nLine3.";
XmlWriterSettings xws = new XmlWriterSettings();
xws.NewLineHandling = NewLineHandling.Entitize;
XDocument doc = new XDocument(new XElement("root",
new XAttribute("test", attValue),
elementValue));
using (XmlWriter xw = XmlWriter.Create(fileName, xws))
{
doc.Save(xw);
}
doc = XDocument.Load(fileName);
Console.WriteLine("att value: {0}; element value: {1}.",
attValue == doc.Root.Attribute("test").Value,
elementValue == doc.Root.Value);
In that example the value are preserved in the round trip of saving and loading as the output of the sample is "att value: True; element value: True."
Heres a useful link I found for parsing an Xml string with carraige returns, line feeds in it.
howto-correctly-parse-using-xelementparse-for-strings-that-contain-newline-character-in
It may help those who are parsing an Xml string.
For those who can't be bothered to click it says use an XmlTextReader instead
XmlTextReader xtr = new XmlTextReader(new StringReader(xml));
XElement items = XElement.Load(xtr);
foreach (string desc in items.Elements("Item").Select(i => (string)i.Attribute("Description")))
{
Console.WriteLine("|{0}|", desc);
}
I'm using XmlTextWriter and its WriteElementString method, for example:
XmlTextWriter writer = new XmlTextWriter("filename.xml", null);
writer.WriteStartElement("User");
writer.WriteElementString("Username", inputUserName);
writer.WriteElementString("Email", inputEmail);
writer.WriteEndElement();
writer.Close();
The expected XML output is:
<User>
<Username>value</Username>
<Email>value</Email>
</User>
However, if for example inputEmail is empty, the result XML I get as as follows:
<User>
<Username>value</Username>
<Email/>
</User>
Whereas I would expect it to be:
<User>
<Username>value</Username>
<Email></Email>
</User>
What am I doing wrong? Is there a way to achieve my expected result in a simple way using XmlTextWriter?
Your output is correct. An element with no content should be written as <tag/>.
You can force the use of the full tag by calling WriteFullEndElement()
writer.WriteStartElement("Email");
writer.WriteString(inputEmail);
writer.WriteFullEndElement();
That will output <Email></Email> when inputEmail is empty.
If you want to do that more than once, you could create an extension method:
public static void WriteFullElementString(this XmlTextWriter writer,
string localName,
string value)
{
writer.WriteStartElement(localName);
writer.WriteString(value);
writer.WriteFullEndElement();
}
Then your code would become:
writer.WriteStartElement("User");
writer.WriteFullElementString("Username", inputUserName);
writer.WriteFullElementString("Email", inputEmail);
writer.WriteEndElement();
It doesn't fail <Tag/> is just a shortcut for <Tag></Tag>
Your code should be:
using (XmlWriter writer = XmlWriter.Create("filename.xml"))
{
writer.WriteStartElement("User");
writer.WriteElementString("Username", inputUserName);
writer.WriteElementString("Email", inputEmail);
writer.WriteEndElement();
}
This avoids resource leaks in case of exceptions, and uses the proper way to create an XmlReader (since .NET 2.0).
Leaving this here in case someone needs it; since none of the answers above solved it for me, or seemed like overkill.
FileStream fs = new FileStream("file.xml", FileMode.Create);
XmlWriterSettings settings = new XmlWriterSettings();
settings.Indent = true;
XmlWriter w = XmlWriter.Create(fs, settings);
w.WriteStartDocument();
w.WriteStartElement("tag1");
w.WriteStartElement("tag2");
w.WriteAttributeString("attr1", "val1");
w.WriteAttributeString("attr2", "val2");
w.WriteFullEndElement();
w.WriteEndElement();
w.WriteEndDocument();
w.Flush();
fs.Close();
The trick was to set the XmlWriterSettings.Indent = true and add it to the XmlWriter.
Edit:
Alternatively you can also use
w.Formatting = Formatting.Indented;
instead of adding an XmlWriterSettings.
Tried solving this with another approach, might need optimization.
public class SerializeConfig<T> where T : class
{
public static string Serialize(T type)
{
var settings = new XmlWriterSettings
{
Encoding = Encoding.UTF8,
Indent = true,
OmitXmlDeclaration = true
};
var sb = new StringBuilder();
var serializer = new XmlSerializer(type.GetType());
using (var writer = XmlWriter.Create(sb, settings))
{
serializer.Serialize(writer, type);
}
return sb.ToString().FixXmlClosingTags();
}
}
internal static class InsertStringExtention
{
public static string FixXmlClosingTags(this string xmlString)
{
var sb = new StringBuilder();
var xmlTags = xmlString.Split('\r');
foreach (var tag in xmlTags)
{
if (tag.Contains("/>"))
{
var tagValue = tag.Replace("<", "").Replace("/>", "").Trim();
var firstPart = tag.Substring(0, tag.IndexOf('<'));
var newTag = $"{firstPart}<{tagValue}></{tagValue}>";
sb.Append(newTag);
}
else
{
sb.Append(tag);
}
}
return sb.ToString();
}
}