private static ConstantExpression GetScalarValue(FilterValue value, Type type)
{
var converter = TypeDescriptor.GetConverter(type);
if (converter == null)
{
throw new InvalidOperationException($"Couldn't find type converter for type '{type.Name}'.");
}
return(Expression.Constant(converter.ConvertFromString(value.Value)));
}
public override Expression Visit(Expression node)
{
if (IsTerminal(node))
{
return(node);
}
switch (node.NodeType)
{
case ExpressionType.Constant:
return(base.Visit(node));
default:
Value = GetValue(Evaluate(node));
return(node);
}
}
private static ConstantExpression GetVectorValue(FilterValue value, Type type)
{
var converter = TypeDescriptor.GetConverter(type);
if (converter == null)
{
throw new InvalidOperationException($"Couldn't find type converter for type '{type.Name}'.");
}
var values = value.Value.Split(',');
var vector = Array.CreateInstance(type, values.Length);
for (var index = 0; index < values.Length; index++)
{
vector.SetValue(converter.ConvertFromString(values[index]), index);
}
return(Expression.Constant(vector));
}
public static Filter Parse(string text)
{
var or = Or.Match(text);
if (or.Success)
{
return(new LogicalFilter
(
Parse(or.Groups["Left"].Value),
LogicalOperator.Or,
Parse(or.Groups["Right"].Value)
));
}
var and = And.Match(text);
if (and.Success)
{
return(new LogicalFilter
(
Parse(and.Groups["Left"].Value),
LogicalOperator.And,
Parse(and.Groups["Right"].Value)
));
}
var predicate = Predicate.Match(text);
if (predicate.Success)
{
return(new PredicateFilter
(
FilterProperty.Parse(predicate.Groups["Property"].Value),
PredicateOperator.Parse(predicate.Groups["Predicate"].Value),
FilterValue.Parse(predicate.Groups["Value"].Value)
));
}
throw new ArgumentException($"Couldn't parse filter '{text}'.");
}
public void Equal(FilterProperty left, FilterValue value) =>
_filter.Append($"{left}{PredicateOperatorString.Equal}{value}");
public void Any(FilterProperty property, FilterValue value) =>
_filter.Append($"{property}{PredicateOperatorString.Contains}{value}");
protected override Expression VisitConstant(ConstantExpression node)
{
Value = GetValue(node.Value);
return(node);
}
public FilterExpressionBuilder <T> NotEqual(FilterProperty property, FilterValue value) => Predicate(Expression.NotEqual, property, value, () => Expression.Constant(true));
public FilterExpressionBuilder <T> LessThanOrEqual(FilterProperty property, FilterValue value) => Predicate(Expression.LessThanOrEqual, property, value);
public PredicateFilter(FilterProperty property, PredicateOperator predicate, FilterValue value)
{
Property = property;
Predicate = predicate;
Value = value;
}
public FilterExpressionBuilder <T> Any(FilterProperty property, FilterValue value) => Contains(FilterInfo.Any, property, value);
private FilterExpressionBuilder <T> Predicate(Func <Expression, Expression, Expression> factory, Expression property, FilterValue value, Func <Expression> fallback)
{
// TODO add stronger exception handling and conditional support for fallback
Expression expression;
try
{
expression = factory(property, GetScalarValue(value, property.Type));
}
catch (FormatException e)
{
expression = fallback?.Invoke() ?? throw e;
}
_expressions.Push(expression);
return(this);
}
private FilterExpressionBuilder <T> Predicate(Func <Expression, Expression, Expression> factory, FilterProperty property, FilterValue value, Func <Expression> fallback = null) => Predicate(factory, GetProperty(property), value, fallback);
private FilterExpressionBuilder <T> Contains(MethodInfo method, FilterProperty property, FilterValue value)
{
var member = GetProperty(property);
var collection = member.Type.Name == typeof(ICollection <>).Name
? member.Type
: member.Type.GetTypeInfo().GetInterface(typeof(ICollection <>).Name);
if (collection == null)
{
throw new InvalidOperationException($"Property '{property}' does not implement '{typeof(ICollection<>)}'.");
}
var type = collection.GetTypeInfo().GetGenericArguments().Single();
var item = Expression.Parameter(type);
var contains = Expression.Lambda(Expression.Call(null, FilterInfo.Contains.MakeGenericMethod(type), member, item), item);
var call = Expression.Call(null, method.MakeGenericMethod(type), GetVectorValue(value, type), contains);
_expressions.Push(call);
return(this);
}
public void LessThan(FilterProperty property, FilterValue value) =>
_filter.Append($"{property}{PredicateOperatorString.LessThan}{value}");
public void NotEqual(FilterProperty property, FilterValue value) =>
_filter.Append($"{property}{PredicateOperatorString.NotEqual}{value}");
public FilterExpressionBuilder <T> GreaterThan(FilterProperty property, FilterValue value) => Predicate(Expression.GreaterThan, property, value);