Xml – Find through multiple attributes in XML

searchxmlxml-attribute

I'm trying to search multiple attributes in XML :

<APIS>
  <API Key="00001">
    <field Username="username1" UserPassword="password1" FileName="Filename1.xml"/>
    <field Username="username2" UserPassword="password2" FileName="Filename2.xml"/>
    <field Username="username3" UserPassword="password3" FileName="Filename3.xml"/>
  </API>
</APIS>

I need to check if in the "field" the Username AND UserPassword values are both what I am comparing with my Dataset values, is there a way where I can check multiple attributes (AND condition) without writing my own logic of using Flags and breaking out of loops.

Is there a built in function of XMLDoc that does it? Any help would be appreciated!

Best Solution

To search for what you want in the snippet of XML you provided, you would need the following XPath expression:

/APIS/API/field[@Username='username1' and @UserPassword='password1']

This would either return something, if user name and password match - or not if they don't.

Of couse the XPath expression is just a string - you can build it dynamically with values that were entered into a form field, for example.

If you tell what language/environment you are in, code samples posted here will likely get more specific.

This is a way to do it in C# (VB.NET is analogous):

// make sure the following line is included in your class
using System.Xml;

XmlDocument xmldoc = new XmlDocument();
xmldoc.Load("your XML string or file");

string xpath = "/APIS/API/field[@Username='{0}' and @UserPassword='{1}']";
string username = "username1";
string password = "password1";

xpath = String.Format(xpath, username, password);
XmlNode userNode = xmldoc.SelectSingleNode(xpath);

if (userNode != null)
{
  // found something with given user name and password
}
else
{
  // username or password incorrect
}

Be aware that neither user names nor passwords can contain single quotes, or the above example will fail. Here is some info on this peculiarity.

There is also a How-To from Microsoft available: HOW TO: Use the System.Xml.XmlDocument Class to Execute XPath Queries in Visual C# .NET

Related Solutions

Unix – Use grep –exclude/–include syntax to not grep through certain files

Use the shell globbing syntax:

grep pattern -r --include=\*.cpp --include=\*.h rootdir

The syntax for --exclude is identical.

Note that the star is escaped with a backslash to prevent it from being expanded by the shell (quoting it, such as --include="*.cpp", would work just as well). Otherwise, if you had any files in the current working directory that matched the pattern, the command line would expand to something like grep pattern -r --include=foo.cpp --include=bar.cpp rootdir, which would only search files named foo.cpp and bar.cpp, which is quite likely not what you wanted.

Update 2021-03-04

I've edited the original answer to remove the use of brace expansion, which is a feature provided by several shells such as Bash and zsh to simplify patterns like this; but note that brace expansion is not POSIX shell-compliant.

The original example was:

grep pattern -r --include=\*.{cpp,h} rootdir

to search through all .cpp and .h files rooted in the directory rootdir.

Xml – What characters do I need to escape in XML documents

If you use an appropriate class or library, they will do the escaping for you. Many XML issues are caused by string concatenation.

XML escape characters

There are only five:

"   &quot;
'   &apos;
<   &lt;
>   &gt;
&   &amp;

Escaping characters depends on where the special character is used.

The examples can be validated at the W3C Markup Validation Service.

Text

The safe way is to escape all five characters in text. However, the three characters ", ' and > needn't be escaped in text:

<?xml version="1.0"?>
<valid>"'></valid>

Attributes

The safe way is to escape all five characters in attributes. However, the > character needn't be escaped in attributes:

<?xml version="1.0"?>
<valid attribute=">"/>

The ' character needn't be escaped in attributes if the quotes are ":

<?xml version="1.0"?>
<valid attribute="'"/>

Likewise, the " needn't be escaped in attributes if the quotes are ':

<?xml version="1.0"?>
<valid attribute='"'/>

Comments

All five special characters must not be escaped in comments:

<?xml version="1.0"?>
<valid>
<!-- "'<>& -->
</valid>

CDATA

All five special characters must not be escaped in CDATA sections:

<?xml version="1.0"?>
<valid>
<![CDATA["'<>&]]>
</valid>

Processing instructions

All five special characters must not be escaped in XML processing instructions:

<?xml version="1.0"?>
<?process <"'&> ?>
<valid/>

XML vs. HTML

HTML has its own set of escape codes which cover a lot more characters.