Attributes

Working with Attributes

The main class for Attribute processing is AttributeTypeType. CAEX elements which can have Attributes assigned, implement the Interface IObjectWithAttributes. Extension methods for Attributes are defined in ObjectWithAttributes.

This topic contains the following examples:

• Encoding and Decoding of Attribute values according to the defined Attribute-Datatype
• Structure Attributes

The programming examples show how to work with attribute values and attribute-datatypes and how to work with structures. Please note that when using attribute paths, attribute names may need to be enclosed in square brackets if a path separator occurs in an attribute name, or escape characters must be used to indicate square brackets contained in attribute names.

Attribute Values and Attribute Datatypes

using Aml.Engine.CAEX;
void AttributeValuesAndDataTypes(CAEXDocument document)
{
    // adds a raw attribute - without value and datatype - to an element
    var instanceHierarchy = document.CAEXFile.InstanceHierarchy.Append("ih1");
    var element1 = instanceHierarchy.InternalElement.Append("element1");
    var attribute1 = element1.Attribute.Append("attribute1");

    // Attributes provide 'Value'- and 'AttributeDataType'- properties
    // The value property is of type 'string' which means that the user
    // has to define the correct xml format for the desired data type himself.

    // storing a date time value, using 'Value' and 'AttributeDataType'.
    // The standard .NET class XmlConvert provides Xml decoding and encoding methods.
    // The ClrToXmlType method converts the ClrType to a XSD datatype.
    
    attribute1.Value = System.Xml.XmlConvert.ToString(DateTime.Now, System.Xml.XmlDateTimeSerializationMode.Local);
    attribute1.AttributeDataType = AttributeTypeType.ClrToXmlType(typeof(DateTime));

    // alternative methods to define the AttributeDataType:
    attribute1.SetAttributeDataType (DateTime.Now);     // sets the type to the XmlType of the object type
    attribute1.SetAttributeDataType (typeof(DateTime)); // sets the type to the XmlType of the ClrType
	
    // Attributes provide the 'AttributeValue'- property (also 'DefaultAttributeValue')
    // This property selects the correct xml encoding and decoding, depending of the assigned
    // AttributeDataType.
    attribute1.AttributeValue = DateTime.Now;
    attribute1.DefaultAttributeValue = DateTime.MinValue;

    // ensure, that the saved value preserves the data type
    Debug.Assert(attribute1.AttributeValue is DateTime);

    // assignment of a value which doesn't fit to the defined AttributeDataType is rejected
    attribute1.AttributeValue = 1.0;
    Debug.Assert(attribute1.AttributeValue.Equals(1.0)==false);

    // reset the datatype to change the value and type
    attribute1.AttributeDataType = AttributeTypeType.ClrToXmlType(typeof(double)); 
    attribute1.AttributeValue = 1.0;

    // ensure, that the saved value preserves the changed data type
    Debug.Assert(attribute1.AttributeValue is double);
	
    // if no AttributeDataType is defined for an attribute it is selected 
    // in the first assignment of a value	
    var attribute2 = element1.Attribute.Append("attribute2");
    attribute2.AttributeValue = 1.0; // AttributeDataType is set to xs:double		
}

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Structure Attributes

using Aml.Engine.CAEX;
using Aml.Engine.CAEX.Extensions;

void CreateStructure ()
{	
    var instanceHierarchy = document.CAEXFile.InstanceHierarchy.Append("ih1");
    var element1 = instanceHierarchy.InternalElement.Append("element1");
    // adds a structure attribute to an element	
    var size = element1.Attribute.Append("Size");	
	
    // adds a With Attribute to the Size structure, setting the value 
    // and the datatype to the value-type double using an extension method
    var width  = size.SetAttributeValue("Width", 10.0);	
	
    // adds a Height Attribute to the Size structure, setting the value 
    // and the datatype to the value-type double using an extension method
    var height = size.SetAttributeValue("Height", 20.0);
	
    // using attribute paths
    element1.SetAttributeValue ("Size/With", 25.0);  // only for CAEX 3.0 documents	
    element1.SetAttributeValue ("Size.With", 25.0);  // only for CAEX 2.15 documents
	
    // using indexer to access structure elements
    element1.Attribute["Size","Width"]=25.0;// for all CAEX versions
	
    // using path as index to access the structure element
    element1.Attribute ["Size/With"]=25.0;  // only for a a CAEX 3.0 document
    element1.Attribute ["Size.With"]=25.0;  // only for a CAEX 2.15 document
}

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See also:

AttributeTypeType

AttributeValue

ObjectWithAttributes

CAEXPathBuilder