/// <summary>
/// Main evaluation method which is divided in two phases: Argument processing and
/// Function evaluation.
/// </summary>
/// <param name="context">The evaluation context instance.</param>
/// <returns>The result of the evaluation in an EvaluationValue instance.</returns>
public virtual EvaluationValue Evaluate(EvaluationContext context)
{
if (context == null)
{
throw new ArgumentNullException("context");
}
// Validate the function exists
context.Trace("Calling function: {0}", _applyBase.FunctionId);
IFunction function = EvaluationEngine.GetFunction(_applyBase.FunctionId);
if (function == null)
{
context.Trace("ERR: function not found {0}", _applyBase.FunctionId);
context.ProcessingError = true;
return(EvaluationValue.Indeterminate);
}
// Process the arguments.
FunctionParameterCollection arguments = ProcessArguments(context, new ExpressionCollection((ExpressionReadWriteCollection)_applyBase.Arguments));
// Call the function with the arguments processed.
EvaluationValue returnValue = EvaluationEngine.EvaluateFunction(context, function, arguments.ToArray());
return(returnValue);
}
/// <summary>
/// Evaluates the rule contents.
/// </summary>
/// <param name="context">The evaluation context instance.</param>
/// <returns>A decission for this evalauation.</returns>
public Decision Evaluate(EvaluationContext context)
{
if (context == null)
{
throw new ArgumentNullException("context");
}
context.Trace("Evaluating rule: {0}", _rule.Description);
context.AddIndent();
context.CurrentRule = this;
try
{
// Validate the Target element
TargetEvaluationValue targetEvaluation = Match(context);
// If the target matches the conditions ar evaluated
EvaluationValue conditionEvaluation = EvaluationValue.True;
if (_rule.HasCondition)
{
// Evaluate the condition
conditionEvaluation = _condition.Evaluate(context);
}
else
{
context.Trace("Rule does not have a condition");
}
// Decite the final rule evaluation value
if (targetEvaluation == TargetEvaluationValue.Indeterminate || conditionEvaluation.IsIndeterminate)
{
_evaluationValue = Decision.Indeterminate;
}
else if (targetEvaluation == TargetEvaluationValue.Match && conditionEvaluation.BoolValue)
{
_evaluationValue = ((_rule.Effect == Effect.Permit) ? Decision.Permit : Decision.Deny);
}
else if ((targetEvaluation == TargetEvaluationValue.NoMatch) ||
(targetEvaluation == TargetEvaluationValue.Match && !conditionEvaluation.BoolValue))
{
_evaluationValue = Decision.NotApplicable;
}
// Return the value
context.Trace("Rule: {0}", _evaluationValue);
return(_evaluationValue);
}
finally
{
context.RemoveIndent();
context.CurrentRule = null;
}
}
/// <summary>
/// THe argument processing method resolves all the attribute designators, attribute
/// selectors. If there is an internal Apply it will be evaulated within this method.
/// </summary>
/// <remarks>All the processed arguments are converted into an IFunctionParameter instance
/// because this is the only value that can be used to call a function.</remarks>
/// <param name="context">The evaluation context instance.</param>
/// <param name="arguments">The arguments to process.</param>
/// <returns>A list of arguments ready to be used by a function.</returns>
private FunctionParameterCollection ProcessArguments(EvaluationContext context, ExpressionCollection arguments)
{
context.Trace("Processing arguments");
context.AddIndent();
// Create a list to return the processed values.
var processedArguments = new FunctionParameterCollection();
// Iterate through the arguments, the IExpressionType is a mark interface
foreach (IExpression arg in arguments)
{
var apply = arg as ApplyElement;
if (apply != null)
{
context.Trace("Nested apply");
// There is a nested apply un this policy a new Apply will be created and also
// evaluated. It's return value will be used as the processed argument.
var childApply = new Apply(apply);
// Evaluate the Apply
EvaluationValue retVal = childApply.Evaluate(context);
context.TraceContextValues();
// If the results were Indeterminate the Indeterminate value will be placed in
// the processed arguments, later another method will validate the parameters
// and cancel the evaluation propperly.
if (!retVal.IsIndeterminate)
{
if (!context.IsMissingAttribute)
{
processedArguments.Add(retVal);
}
}
else
{
processedArguments.Add(retVal);
}
}
else
{
var write = arg as FunctionElementReadWrite;
if (write != null)
{
// Search for the function and place it in the processed arguments.
var functionId = new FunctionElement(write.FunctionId, write.SchemaVersion);
context.Trace("Function {0}", functionId.FunctionId);
IFunction function = EvaluationEngine.GetFunction(functionId.FunctionId);
if (function == null)
{
context.Trace("ERR: function not found {0}", _applyBase.FunctionId);
context.ProcessingError = true;
processedArguments.Add(EvaluationValue.Indeterminate);
}
else
{
processedArguments.Add(function);
}
}
else if (arg is VariableReferenceElement)
{
var variableRef = arg as VariableReferenceElement;
var variableDef = context.CurrentPolicy.VariableDefinition[variableRef.VariableId] as VariableDefinition;
context.TraceContextValues();
Debug.Assert(variableDef != null, "variableDef != null");
processedArguments.Add(!variableDef.IsEvaluated ? variableDef.Evaluate(context) : variableDef.Value);
}
else
{
var readWrite = arg as AttributeValueElementReadWrite;
if (readWrite != null)
{
// The AttributeValue does not need to be processed
context.Trace("Attribute value {0}", arg.ToString());
processedArguments.Add(new AttributeValueElement(readWrite.DataType, readWrite.Contents, readWrite.SchemaVersion));
}
else
{
var des = arg as AttributeDesignatorBase;
if (des != null)
{
// Resolve the AttributeDesignator using the EvaluationEngine public methods.
context.Trace("Processing attribute designator: {0}", arg.ToString());
var attrDes = des;
BagValue bag = EvaluationEngine.Resolve(context, attrDes);
// If the attribute was not resolved by the EvaluationEngine search the
// attribute in the context document, also using the EvaluationEngine public
// methods.
if (bag.BagSize == 0)
{
if (arg is SubjectAttributeDesignatorElement)
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute(context, attrDes);
if (attrib != null)
{
context.Trace("Adding subject attribute designator: {0}", attrib.ToString());
bag.Add(attrib);
break;
}
}
else if (arg is ResourceAttributeDesignatorElement)
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute(context, attrDes);
if (attrib != null)
{
context.Trace("Adding resource attribute designator {0}", attrib.ToString());
bag.Add(attrib);
}
}
else if (arg is ActionAttributeDesignatorElement)
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute(context, attrDes);
if (attrib != null)
{
context.Trace("Adding action attribute designator {0}", attrib.ToString());
bag.Add(attrib);
}
}
else if (arg is EnvironmentAttributeDesignatorElement)
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute(context, attrDes);
if (attrib != null)
{
context.Trace("Adding environment attribute designator {0}", attrib.ToString());
bag.Add(attrib);
}
}
}
// If the argument was not found and the attribute must be present this is
// a MissingAttribute situation so set the flag. Otherwise add the attribute
// to the processed arguments.
if (bag.BagSize == 0 && attrDes.MustBePresent)
{
context.Trace("Attribute is missing");
context.IsMissingAttribute = true;
context.AddMissingAttribute(attrDes);
}
else
{
processedArguments.Add(bag);
}
}
else
{
var @base = arg as AttributeSelectorElement;
if (@base != null)
{
// Resolve the XPath query using the EvaluationEngine public methods.
context.Trace("Attribute selector");
try
{
BagValue bag = EvaluationEngine.Resolve(context, @base);
if (bag.Elements.Count == 0 && @base.MustBePresent)
{
context.Trace("Attribute is missing");
context.IsMissingAttribute = true;
context.AddMissingAttribute(@base);
}
else
{
processedArguments.Add(bag);
}
}
catch (EvaluationException e)
{
context.Trace("ERR: {0}", e.Message);
processedArguments.Add(EvaluationValue.Indeterminate);
context.ProcessingError = true;
}
}
}
}
}
}
}
context.RemoveIndent();
return(processedArguments);
}
/// <summary>
/// Evaluates the variable into a value.
/// </summary>
/// <param name="context">The contex of the evaluation.</param>
/// <returns>The value of the function.</returns>
public EvaluationValue Evaluate(EvaluationContext context)
{
if (context == null)
{
throw new ArgumentNullException("context");
}
context.Trace("Evaluating variable");
context.AddIndent();
try
{
if (_variableDefinition.Expression is ApplyElement)
{
context.Trace("Apply within condition.");
// There is a nested apply un this policy a new Apply will be created and also
// evaluated. It's return value will be used as the processed argument.
Apply childApply = new Apply((ApplyElement)_variableDefinition.Expression);
// Evaluate the Apply
_value = childApply.Evaluate(context);
context.TraceContextValues();
return(_value);
}
else if (_variableDefinition.Expression is FunctionElement)
{
throw new NotImplementedException("FunctionElement"); //TODO:
}
else if (_variableDefinition.Expression is VariableReferenceElement)
{
var variableRef = _variableDefinition.Expression as VariableReferenceElement;
var variableDef = context.CurrentPolicy.VariableDefinition[variableRef.VariableId] as VariableDefinition;
context.TraceContextValues();
if (!variableDef.IsEvaluated)
{
return(variableDef.Evaluate(context));
}
else
{
return(variableDef.Value);
}
}
else if (_variableDefinition.Expression is AttributeValueElementReadWrite)
{
// The AttributeValue does not need to be processed
context.Trace("Attribute value {0}", _variableDefinition.Expression.ToString());
var att = (AttributeValueElementReadWrite)_variableDefinition.Expression;
var attributeValue = new AttributeValueElement(att.DataType, att.Contents, att.SchemaVersion);
_value = new EvaluationValue(
attributeValue.GetTypedValue(attributeValue.GetType(context), 0),
attributeValue.GetType(context));
return(_value);
}
else if (_variableDefinition.Expression is AttributeDesignatorBase)
{
// Resolve the AttributeDesignator using the EvaluationEngine public methods.
context.Trace("Processing attribute designator: {0}", _variableDefinition.Expression.ToString());
var attrDes = (AttributeDesignatorBase)_variableDefinition.Expression;
BagValue bag = EvaluationEngine.Resolve(context, attrDes);
// If the attribute was not resolved by the EvaluationEngine search the
// attribute in the context document, also using the EvaluationEngine public
// methods.
if (bag.BagSize == 0)
{
if (_variableDefinition.Expression is SubjectAttributeDesignatorElement)
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute(context, attrDes);
if (attrib != null)
{
context.Trace("Adding subject attribute designator: {0}", attrib.ToString());
bag.Add(attrib);
}
}
else if (_variableDefinition.Expression is ResourceAttributeDesignatorElement)
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute(context, attrDes);
if (attrib != null)
{
context.Trace("Adding resource attribute designator {0}", attrib.ToString());
bag.Add(attrib);
}
}
else if (_variableDefinition.Expression is ActionAttributeDesignatorElement)
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute(context, attrDes);
if (attrib != null)
{
context.Trace("Adding action attribute designator {0}", attrib.ToString());
bag.Add(attrib);
}
}
else if (_variableDefinition.Expression is EnvironmentAttributeDesignatorElement)
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute(context, attrDes);
if (attrib != null)
{
context.Trace("Adding environment attribute designator {0}", attrib.ToString());
bag.Add(attrib);
}
}
}
// If the argument was not found and the attribute must be present this is
// a MissingAttribute situation so set the flag. Otherwise add the attribute
// to the processed arguments.
if (bag.BagSize == 0 && attrDes.MustBePresent)
{
context.Trace("Attribute is missing");
context.IsMissingAttribute = true;
context.AddMissingAttribute(attrDes);
_value = EvaluationValue.Indeterminate;
}
else
{
_value = new EvaluationValue(bag, bag.GetType(context));
}
return(_value);
}
else if (_variableDefinition.Expression is AttributeSelectorElement)
{
// Resolve the XPath query using the EvaluationEngine public methods.
context.Trace("Attribute selector");
try
{
var attributeSelector = (AttributeSelectorElement)_variableDefinition.Expression;
BagValue bag = EvaluationEngine.Resolve(context, attributeSelector);
if (bag.Elements.Count == 0 && attributeSelector.MustBePresent)
{
context.Trace("Attribute is missing");
context.IsMissingAttribute = true;
context.AddMissingAttribute(attributeSelector);
_value = EvaluationValue.Indeterminate;
}
else
{
_value = new EvaluationValue(bag, bag.GetType(context));
}
}
catch (EvaluationException e)
{
context.Trace("ERR: {0}", e.Message);
context.ProcessingError = true;
_value = EvaluationValue.Indeterminate;
}
return(_value);
}
throw new NotSupportedException("internal error");
}
finally
{
_isEvaluated = true;
context.RemoveIndent();
}
}
/// <summary>
/// Evaluates the target items and return wether the target applies to the context or not.
/// </summary>
/// <param name="context">The evaluation context instance.</param>
/// <param name="targetItem">The target item in the context document.</param>
/// <returns></returns>
public virtual TargetEvaluationValue Evaluate(EvaluationContext context, ctx.TargetItemBase targetItem)
{
if (context == null)
{
throw new ArgumentNullException("context");
}
if (_targetItems.IsAny)
{
context.Trace("IsAny");
return(TargetEvaluationValue.Match);
}
_evaluationValue = TargetEvaluationValue.NoMatch;
//Match TargetItem
foreach (TargetItemBase polItem in _targetItems.ItemsList)
{
foreach (TargetMatchBase match in polItem.Match)
{
_evaluationValue = TargetEvaluationValue.NoMatch;
context.Trace("Using function: {0}", match.MatchId);
IFunction matchFunction = EvaluationEngine.GetFunction(match.MatchId);
if (matchFunction == null)
{
context.Trace("ERR: function not found {0}", match.MatchId);
context.ProcessingError = true;
return(TargetEvaluationValue.Indeterminate);
}
else if (matchFunction.Returns == null)
{
// Validates the function return value
context.Trace("ERR: The function '{0}' does not defines it's return value", match.MatchId);
context.ProcessingError = true;
return(TargetEvaluationValue.Indeterminate);
}
else if (matchFunction.Returns != DataTypeDescriptor.Boolean)
{
context.Trace("ERR: Function does not return Boolean a value");
context.ProcessingError = true;
return(TargetEvaluationValue.Indeterminate);
}
else
{
Context.AttributeElement attribute = EvaluationEngine.Resolve(context, match, targetItem);
if (attribute != null)
{
context.Trace("Attribute found, evaluating match function");
try
{
EvaluationValue returnValue = EvaluationEngine.EvaluateFunction(context, matchFunction, match.AttributeValue, attribute);
_evaluationValue = returnValue.BoolValue ? TargetEvaluationValue.Match : TargetEvaluationValue.NoMatch;
}
catch (EvaluationException e)
{
context.Trace("ERR: {0}", e.Message);
_evaluationValue = TargetEvaluationValue.Indeterminate;
}
}
// Validate MustBePresent
if (match.AttributeReference.MustBePresent)
{
if (context.IsMissingAttribute)
{
context.Trace("Attribute not found and must be present");
_evaluationValue = TargetEvaluationValue.Indeterminate;
}
}
if (context.ProcessingError)
{
_evaluationValue = TargetEvaluationValue.Indeterminate;
}
// Do not iterate if the value was found
if (_evaluationValue != TargetEvaluationValue.Match)
{
break;
}
}
}
// Do not iterate if the value was found
if (_evaluationValue == TargetEvaluationValue.Match)
{
return(_evaluationValue);
}
}
return(_evaluationValue);
}
/// <summary>
/// This method overrides the ApplyBase method in order to provide extra validations
/// required in the condition evaluation, for example the final return value should be a
/// boolean value.
/// </summary>
/// <param name="context">The evaluation context instance.</param>
/// <returns>The EvaluationValue with the results of the condition evaluation.</returns>
public override EvaluationValue Evaluate(EvaluationContext context)
{
if (context == null)
{
throw new ArgumentNullException("context");
}
context.Trace("Evaluating condition");
context.AddIndent();
try
{
// Iterate through the arguments, the IExpressionType is a mark interface
foreach (IExpression arg in ApplyDefinition.Arguments)
{
if (arg is ApplyElement)
{
context.Trace("Apply within condition.");
// There is a nested apply un this policy a new Apply will be created and also
// evaluated. It's return value will be used as the processed argument.
var childApply = new Apply((ApplyElement)arg);
// Evaluate the Apply
EvaluationValue retVal = childApply.Evaluate(context);
return(retVal);
}
else if (arg is FunctionElementReadWrite)
{
throw new NotImplementedException("FunctionElement"); //TODO:
}
else if (arg is VariableReferenceElement)
{
var variableRef = arg as VariableReferenceElement;
var variableDef = context.CurrentPolicy.VariableDefinition[variableRef.VariableId] as VariableDefinition;
Debug.Assert(variableDef != null, "variableDef != null");
if (!variableDef.IsEvaluated)
{
return(variableDef.Evaluate(context));
}
else
{
return(variableDef.Value);
}
}
else if (arg is AttributeValueElementReadWrite)
{
// The AttributeValue does not need to be processed
context.Trace("Attribute value {0}", arg.ToString());
var attributeValue = new AttributeValueElement(((AttributeValueElementReadWrite)arg).DataType, ((AttributeValueElementReadWrite)arg).Contents, ((AttributeValueElementReadWrite)arg).SchemaVersion);
return(new EvaluationValue(
attributeValue.GetTypedValue(attributeValue.GetType(context), 0),
attributeValue.GetType(context)));
}
else if (arg is AttributeDesignatorBase)
{
// Returning an empty bag, since the condition is not supposed to work with a bag
context.Trace("Processing attribute designator: {0}", arg.ToString());
var attrDes = (AttributeDesignatorBase)arg;
var bag = new BagValue(EvaluationEngine.GetDataType(attrDes.DataType));
return(new EvaluationValue(bag, bag.GetType(context)));
}
else if (arg is AttributeSelectorElement)
{
// Returning an empty bag, since the condition is not supposed to work with a bag
context.Trace("Attribute selector");
var attrSel = (AttributeSelectorElement)arg;
var bag = new BagValue(EvaluationEngine.GetDataType(attrSel.DataType));
return(new EvaluationValue(bag, bag.GetType(context)));
}
}
throw new NotSupportedException("internal error");
}
finally
{
context.TraceContextValues();
context.RemoveIndent();
}
}
/// <summary>
/// This method overrides the ApplyBase method in order to provide extra validations
/// required in the condition evaluation, for example the final return value should be a
/// boolean value.
/// </summary>
/// <param name="context">The evaluation context instance.</param>
/// <returns>The EvaluationValue with the results of the condition evaluation.</returns>
public override EvaluationValue Evaluate(EvaluationContext context)
{
if (context == null)
{
throw new ArgumentNullException("context");
}
EvaluationValue evaluationValue = null;
context.Trace("Evaluating condition...");
context.AddIndent();
try
{
// Get the function instance
IFunction function = EvaluationEngine.GetFunction(ApplyDefinition.FunctionId);
if (function == null)
{
context.Trace("ERR: function not found {0}", ApplyDefinition.FunctionId);
context.ProcessingError = true;
return(EvaluationValue.Indeterminate);
}
// Validates the function return value
if (function.Returns == null)
{
context.Trace("The function '{0}' does not defines it's return value", ApplyDefinition.FunctionId);
evaluationValue = EvaluationValue.Indeterminate;
context.ProcessingError = true;
}
else if (function.Returns != DataTypeDescriptor.Boolean)
{
context.Trace("Function does not return Boolean a value");
evaluationValue = EvaluationValue.Indeterminate;
context.ProcessingError = true;
}
else
{
// Call the ApplyBase method to perform the evaluation.
evaluationValue = base.Evaluate(context);
}
// Validate the results of the evaluation
if (evaluationValue.IsIndeterminate)
{
context.Trace("condition evaluated into {0}", evaluationValue.ToString());
return(evaluationValue);
}
if (!(evaluationValue.Value is bool))
{
context.Trace("condition evaluated into {0}", evaluationValue.ToString());
return(EvaluationValue.Indeterminate);
}
if (evaluationValue.BoolValue)
{
context.Trace("condition evaluated into {0}", evaluationValue.ToString());
return(EvaluationValue.True);
}
else
{
// If the evaluation was false, validate if there was a missin attribute during
// evaluation and return an Indeterminate, otherwise return the False value.
if (context.IsMissingAttribute)
{
context.Trace("condition evaluated into {0}", evaluationValue.ToString());
return(EvaluationValue.Indeterminate);
}
else
{
context.Trace("condition evaluated into {0}", evaluationValue.ToString());
return(EvaluationValue.False);
}
}
}
finally
{
context.TraceContextValues();
context.RemoveIndent();
context.Trace("Condition: {0}", evaluationValue == null ? string.Empty : evaluationValue.ToString());
}
}
/// <summary>
/// Evaluates the variable into a value.
/// </summary>
/// <param name="context">The contex of the evaluation.</param>
/// <returns>The value of the function.</returns>
public EvaluationValue Evaluate(EvaluationContext context)
{
if (context == null) throw new ArgumentNullException("context");
context.Trace("Evaluating variable");
context.AddIndent();
try
{
if (_variableDefinition.Expression is ApplyElement)
{
context.Trace("Apply within condition.");
// There is a nested apply un this policy a new Apply will be created and also
// evaluated. It's return value will be used as the processed argument.
Apply childApply = new Apply((ApplyElement)_variableDefinition.Expression);
// Evaluate the Apply
_value = childApply.Evaluate(context);
context.TraceContextValues();
return _value;
}
else if (_variableDefinition.Expression is FunctionElement)
{
throw new NotImplementedException("FunctionElement"); //TODO:
}
else if (_variableDefinition.Expression is VariableReferenceElement)
{
var variableRef = _variableDefinition.Expression as VariableReferenceElement;
var variableDef = context.CurrentPolicy.VariableDefinition[variableRef.VariableId] as VariableDefinition;
context.TraceContextValues();
if (!variableDef.IsEvaluated)
{
return variableDef.Evaluate(context);
}
else
{
return variableDef.Value;
}
}
else if (_variableDefinition.Expression is AttributeValueElementReadWrite)
{
// The AttributeValue does not need to be processed
context.Trace("Attribute value {0}", _variableDefinition.Expression.ToString());
var att = (AttributeValueElementReadWrite)_variableDefinition.Expression;
var attributeValue = new AttributeValueElement(att.DataType, att.Contents, att.SchemaVersion);
_value = new EvaluationValue(
attributeValue.GetTypedValue(attributeValue.GetType(context), 0),
attributeValue.GetType(context));
return _value;
}
else if (_variableDefinition.Expression is AttributeDesignatorBase)
{
// Resolve the AttributeDesignator using the EvaluationEngine public methods.
context.Trace("Processing attribute designator: {0}", _variableDefinition.Expression.ToString());
var attrDes = (AttributeDesignatorBase)_variableDefinition.Expression;
BagValue bag = EvaluationEngine.Resolve(context, attrDes);
// If the attribute was not resolved by the EvaluationEngine search the
// attribute in the context document, also using the EvaluationEngine public
// methods.
if (bag.BagSize == 0)
{
if (_variableDefinition.Expression is SubjectAttributeDesignatorElement)
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute(context, attrDes);
if (attrib != null)
{
context.Trace("Adding subject attribute designator: {0}", attrib.ToString());
bag.Add(attrib);
}
}
else if (_variableDefinition.Expression is ResourceAttributeDesignatorElement)
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute(context, attrDes);
if (attrib != null)
{
context.Trace("Adding resource attribute designator {0}", attrib.ToString());
bag.Add(attrib);
}
}
else if (_variableDefinition.Expression is ActionAttributeDesignatorElement)
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute(context, attrDes);
if (attrib != null)
{
context.Trace("Adding action attribute designator {0}", attrib.ToString());
bag.Add(attrib);
}
}
else if (_variableDefinition.Expression is EnvironmentAttributeDesignatorElement)
{
ctx.AttributeElement attrib = EvaluationEngine.GetAttribute(context, attrDes);
if (attrib != null)
{
context.Trace("Adding environment attribute designator {0}", attrib.ToString());
bag.Add(attrib);
}
}
}
// If the argument was not found and the attribute must be present this is
// a MissingAttribute situation so set the flag. Otherwise add the attribute
// to the processed arguments.
if (bag.BagSize == 0 && attrDes.MustBePresent)
{
context.Trace("Attribute is missing");
context.IsMissingAttribute = true;
context.AddMissingAttribute(attrDes);
_value = EvaluationValue.Indeterminate;
}
else
{
_value = new EvaluationValue(bag, bag.GetType(context));
}
return _value;
}
else if (_variableDefinition.Expression is AttributeSelectorElement)
{
// Resolve the XPath query using the EvaluationEngine public methods.
context.Trace("Attribute selector");
try
{
var attributeSelector = (AttributeSelectorElement)_variableDefinition.Expression;
BagValue bag = EvaluationEngine.Resolve(context, attributeSelector);
if (bag.Elements.Count == 0 && attributeSelector.MustBePresent)
{
context.Trace("Attribute is missing");
context.IsMissingAttribute = true;
context.AddMissingAttribute(attributeSelector);
_value = EvaluationValue.Indeterminate;
}
else
{
_value = new EvaluationValue(bag, bag.GetType(context));
}
}
catch (EvaluationException e)
{
context.Trace("ERR: {0}", e.Message);
context.ProcessingError = true;
_value = EvaluationValue.Indeterminate;
}
return _value;
}
throw new NotSupportedException("internal error");
}
finally
{
_isEvaluated = true;
context.RemoveIndent();
}
}