public void WhereEqual(MemberExpression expression, ConstantExpression c)
{
if (c.Value == null)
{
// If we want to filter for non-bound values we need to mark the properties as optional.
SparqlVariable so = BuildMemberAccessOptional(expression);
// TODO: If we filter a resource, make sure it has been described with variables in the local scope.
// Comparing with null means the variable is not bound.
PatternBuilder.Filter(e => !e.Bound(so.Name));
}
else if (c.Type.IsValueType || c.Type == typeof(string))
{
if (expression.Member.DeclaringType == typeof(string))
{
BuildMemberAccess(expression);
// If we are comparing a property of string we need to implement SPARQL built-in call on the variable such as STRLEN..
BuildBuiltInCall(expression, e => e == c.AsNumericExpression());
}
else
{
// TODO: The default value for a property may be overridden with the DefaultValue attribute.
object defaultValue = TypeHelper.GetDefaultValue(c.Type);
// If the value IS the default value, WhereEquals includes the default value and therefore includes non-bound values..
if (c.Value.Equals(defaultValue))
{
// If we want to filter for non-bound values we need to mark the properties as optional.
SparqlVariable o = BuildMemberAccessOptional(expression);
// Mark the variable to be coalesced with the default value when selected.
CoalescedVariables[o] = Expression.Constant(defaultValue).AsLiteralExpression();
// Comparing with null means the variable is not bound.
PatternBuilder.Filter(e => e.Variable(o.Name) == c.AsLiteralExpression() || !e.Bound(o.Name));
}
else
{
// If we want to filter bound literal values, we still write them into a variable so they can be selected.
SparqlVariable o = BuildMemberAccess(expression);
PatternBuilder.Filter(e => e.Variable(o.Name) == c.AsLiteralExpression());
}
}
}
else
{
// We are comparing reference types / resources against a bound value here.
SparqlVariable so = BuildMemberAccess(expression);
// TODO: If we filter a resource, make sure it has been described with variables in the local scope.
PatternBuilder.Filter(e => e.Variable(so.Name) == c.AsIriExpression());
}
}
public void WhereNotEqual(SparqlVariable v, ConstantExpression c)
{
if (c.Value == null)
{
PatternBuilder.Filter(e => e.Bound(v.Name));
}
else if (c.Type.IsValueType || c.Type == typeof(string))
{
PatternBuilder.Filter(e => e.Variable(v.Name) != c.AsLiteralExpression());
}
else
{
PatternBuilder.Filter(e => e.Variable(v.Name) != c.AsIriExpression());
}
}
public void WhereResourceNotOfType(SparqlVariable s, Type type)
{
RdfClassAttribute t = type.TryGetCustomAttribute <RdfClassAttribute>();
if (t != null)
{
Uri a = new Uri("http://www.w3.org/1999/02/22-rdf-syntax-ns#type");
SparqlVariable o = VariableGenerator.CreateObjectVariable();
ConstantExpression c = Expression.Constant(t.MappedUri);
PatternBuilder.Where(e => e.Subject(s).PredicateUri(a).Object(o));
PatternBuilder.Filter(e => e.Variable(o.Name) != c.AsIriExpression() || !e.Bound(o.Name));
}
}
