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One flexibility SharePoint has is CAML (Collaborative
Application Markup Language).
CAML it’s a markup language like html that allows developers
to do queries against SharePoint lists, it’s syntax is very easy to understand
and it allows to add logical conditions like Where, Contains, And, Or, etc,
just like a SQL Query.
For one of our projects we have
the need to do a filter on SharePoint
views,
the problem here is that
the view it’s a list containing a CAML Query
with
the filters
the view may have, so in order to filter
the view that’s
already been filtered before, we need to append our filters to
the existing
CAML Query.
That’s not a trivial task because
the where statement in a CAML Query
it’s like this:
<Where>
<And>
<Filter1 />
<Filter2 />
</And>
</Where>
If we want to add a
new logical
operator, like an OR it’s not just as simple as to append
the OR expression like
the following
example:
<Where>
<And>
<Filter1 />
<Filter2 />
</And>
<Or>
<Filter3 />
</Or>
</Where>
But instead
the correct query would be:
<Where>
<Or>
<And>
<Filter1 />
<Filter2 />
</And>
<Filter3 />
</Or>
</Where>
Notice that
the <Filter# /> tags are for explanation purpose
only.
In order to solve this problem we
created a simple component, it has a method that receives
the current query
(could be an empty query also) and appends
the expression you want to that
query.
Example:
string currentQuery = @“
<Where>
<And>
<Contains><FieldRef
Name='Title' /><Value Type='Text'>A</Value></Contains>
<Contains><FieldRef Name='Title' /><Value
Type='Text'>B</Value></Contains>
</And>
</Where>”;
currentQuery
= CAMLQueryBuilder.AppendQuery(
currentQuery,
“<Contains><FieldRef
Name='Title' /><Value Type='Text'>C</Value></Contains>”,
CAMLQueryBuilder.Operators.Or);
The fist parameter this function receives it’s
the actual query,
the second
it’s
the filter you want to add, and
the third it’s
the logical operator, so
basically in this query we want all
the items that
the title contains:
the
character A and B or
the ones that contains
the character C.
The result query is:
<Where>
<Or>
<And>
<Contains><FieldRef
Name='Title' /><Value Type='Text'>A</Value></Contains>
<Contains><FieldRef Name='Title' /><Value
Type='Text'>B</Value></Contains>
</And>
<Contains><FieldRef
Name='Title' /><Value Type='Text'>C</Value></Contains>
</Or>
</Where>
The code:
First of all we have an enumerator inside
the
CAMLQueryBuilder class that has
the two possible
Options And, Or.
public enum Operators { And, Or }
Then we have
the main method that’s
the one that performs
the append of
the filters.
public static string AppendQuery(string
containerQuery, string logicalExpression, Operators logicalOperator){
In this method
the first we do is create a
new
XmlDocument and wrap
the current query (that may be empty) with a
“<Query></Query>” tag, because
the query that comes with
the view
doesn’t have a root element and
the XmlDocument must be a well formatted xml.
XmlDocument queryDoc =
new XmlDocument();
queryDoc.LoadXml("<Query>"
+ containerQuery + "</Query>");
The next step is to
create a
new XmlDocument containing
the logical expression that has
the filter
needed.
XmlDocument logicalExpressionDoc =
new XmlDocument();
logicalExpressionDoc.LoadXml("<root>" + logicalExpression + "</root>");
In these next four lines we extract
the expression from
the recently
created XmlDocument and create an XmlElement.
XmlElement expressionElTemp = (XmlElement)logicalExpressionDoc.SelectSingleNode("/root/*");
XmlElement expressionEl =
queryDoc.CreateElement(expressionElTemp.Name);
expressionEl.InnerXml = expressionElTemp.InnerXml;
Below are
the main steps
in
the component logic.
The first “if” checks if
the actual query doesn’t
contains a “Where” clause. In case there’s no “Where” we add it and append
the
expression.
In case that there’s already a “Where” clause,
we get
the entire statement that’s inside
the “Where” and reorder
the query
removing and appending elements to form
the correct query, that will finally
filter
the list.
XmlElement whereEl;
if (!containerQuery.Contains("Where"))
{
queryDoc.FirstChild.AppendChild(queryDoc.CreateElement("Where"));
queryDoc.SelectSingleNode("/Query/Where").AppendChild(expressionEl);
}
else
{
whereEl = (XmlElement)queryDoc.SelectSingleNode("/Query/Where");
if
(!containerQuery.Contains("<And>")
&&
!containerQuery.Contains("<Or>"))
{
XmlElement
operatorEl = queryDoc.CreateElement(GetName(logicalOperator));
XmlElement existingExpression = (XmlElement)whereEl.SelectSingleNode("/Query/Where/*");
whereEl.RemoveChild(existingExpression);
operatorEl.AppendChild(existingExpression);
operatorEl.AppendChild(expressionEl);
whereEl.AppendChild(operatorEl);
}
else
{
XmlElement
operatorEl = queryDoc.CreateElement(GetName(logicalOperator));
XmlElement existingOperator = (XmlElement)whereEl.SelectSingleNode("/Query/Where/*");
whereEl.RemoveChild(existingOperator);
operatorEl.AppendChild(existingOperator);
operatorEl.AppendChild(expressionEl);
whereEl.AppendChild(operatorEl);
}
}
return queryDoc.FirstChild.InnerXml
}
Finally
the GetName method converts
the Enum option to his string equivalent.
private static string GetName(Operators
logicalOperator)
{
return
Enum.GetName(typeof(Operators), logicalOperator);
}
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This component helped our team a lot using SharePoint 2007 and modifying
the queries, but now in SharePoint 2010; that wouldn’t be needed because of
the
incorporation of LINQ to SharePoint. This
new feature enables
the developers to
do typed queries against SharePoint lists without
the need of writing any CAML
code. But there is still much development to
the 2007 version, so I hope this information is useful for other
members.
Post
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written by Sebastian Rodriguez - Portals and
Collaboration Solutions @ UruIT
