MSDN Magazine - March 2008 - (Page 29)

download on the MSDN® Magazine Web site. You might want to refer to it as the text here walks through the fragments of the procedure. It begins by investigating the parameters, converting the input value as necessary, as shown in Figure 2. Based on the enumerated value you supply, indicating the type of the value, the code attempts to convert the Object value you’ve provided to the correct type. Note that in order for Word 2007 to accept the values, date/time values must be in Universal Time Coordinate (UTC) time (that is, based on Greenwich mean time) and Boolean values must be in lower case. If, after investigating the values, the propertyValueString variable is still Nothing, the code raises an exception back to the caller, ending the procedure. Next, the code uses the Microsoft SDK for Open XML Formats to find the document part and the custom properties part within the package. Compare this code to the code from the original snippet, and you’ll have to agree that the SDK makes it far easier to navigate within the document package: Using wdPackage = _ Packaging.WordprocessingDocument.Open(docName, True) Dim documentPart = wdPackage.MainDocumentPart Dim customPropsPart = wdPackage.CustomFilePropertiesPart End Using trieves the node’s first child element, using the First method (in this case, if the code can’t find the first child element, it raises an exception—the property node must contain an element, and if it doesn’t, the code can’t continue because the document is damaged). If the name of the child element matches the type of the new property value, the code changes the value of the element. If not, the code removes the node and sets the propertyNode variable to Nothing. After this code runs, the propertyNode variable either contains the new value or is set to Nothing, as you see in Figure 4. Figure 2 Checking the Types and Performing Conversions Dim propertyTypeName As String = Nothing Dim propertyValueString As String = Nothing ‘ Calculate the correct type: Select Case propertyType Case PropertyTypes.DateTime propertyTypeName = “filetime” ‘ Make sure you were passed a real date, ‘ and if so, format in the correct way. ‘ The date/time value passed in should ‘ represent a UTC date/time. If TypeOf (propertyValue) Is DateTime Then propertyValueString = String.Format(“{0:s}Z”, _ Convert.ToDateTime(propertyValue)) End If Case PropertyTypes.NumberInteger propertyTypeName = “i4” If TypeOf (propertyValue) Is Integer Then propertyValueString = propertyValue.ToString() End If Case PropertyTypes.NumberDouble propertyTypeName = “r8” If TypeOf propertyValue Is Double Then propertyValueString = propertyValue.ToString() End If Case PropertyTypes.Text propertyTypeName = “lpwstr” propertyValueString = propertyValue.ToString() Case PropertyTypes.YesNo propertyTypeName = “bool” If TypeOf propertyValue Is Boolean Then ‘ Must be lower case! propertyValueString = _ Convert.ToBoolean(propertyValue).ToString().ToLower() End If End Select If propertyValueString Is Nothing Then ‘ If the code wasn’t able to convert the ‘ property to a valid value, throw an exception: Throw New InvalidDataException(“Invalid parameter value.”) End If If the code is able to retrieve a reference to the custom properties part (that is, if the customPropsPart variable isn’t Nothing), the code loads the contents of the part using the XDocument.Load method (see Figure 3), allowing the GetStream method of the part to retrieve the XML contents. If the part doesn’t exist, the code uses the SDK to create the custom properties part. If the part does exist, the code also attempts to retrieve the first property node for which the name attribute matches the property name you’ve specified. Again, compare this to the original code snippet—you’ll be amazed how much easier this technique is. This code statement makes use of LINQ to XML and the Visual Basic axis properties to simplify the XML manipulation: propertyNode = _ (From node In customDoc. . _ Where node.@name = propertyName).FirstOrDefault() The “.” (period) separator indicates a node one level beneath the parent (customDoc). The syntax indicates an element name. The @ syntax indicates an attribute name. These are specific Visual Basic features (in C#, you would need to use the Element or Attribute property of the XDocument object to get the same information). The code also uses the FirstOrDefault LINQ extension method. This method returns the first matching node, or the default value (Nothing) if it finds no match. You could also use the First or Single extension methods, but each of those raises an exception if no match is found. Here, the code handles the case in which no match was found without raising an exception. After this code executes, customPropsPart contains either a reference to the custom properties part, or Nothing. Likewise, propertyNode contains either a reference to the XElement object corresponding to the property you want to modify, or Nothing if the property doesn’t yet exist. If the propertyNode variable isn’t equal to Nothing, the code re- Figure 3 Find the Custom Properties Part and Set Properties Dim customDoc As XDocument = Nothing Dim propertyNode As XElement = Nothing If customPropsPart IsNot Nothing Then ‘ Load the existing custom properties part: customDoc = XDocument.Load( _ New StreamReader(customPropsPart.GetStream())) propertyNode = _ (From node In customDoc. . _ Where node.@name = propertyName).FirstOrDefault() Else customPropsPart = wdPackage.AddCustomFilePropertiesPart End If Advanced Basics march2008 29

Table of Contents Feed for the Digital Edition of MSDN Magazine - March 2008

MSDN Magazine - March 2008 Contents Toolbox CLR Inside Out Data Points Advanced Basics Office Space Introducing ASP.NET MVC Loosen Up CI Server Performance Office Development Test Run Security Briefs Extreme ASP.NET Foundations .NET Matters {End Bracket}

MSDN Magazine - March 2008

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