private static Expression CheckNullOnEnumerableParent(ExpressionParserPieceGroup group, ExpressionParserPieceGroup parent, Expression parentExpression, bool shouldSkipLast)
{
string path = null;
if (shouldSkipLast)
{
path = string.Join(".", group.Pieces.Take(group.Pieces.Count - 1).Select(t => t.Name));
}
else
{
path = string.Join(".", group.Pieces.Select(t => t.Name));
}
if (!string.IsNullOrEmpty(path))
{
var whereExpression = QueryableHelpers.CreateConditionExpression(group.Parameter.Type, path,
ConditionOperators.NotEqual, null, QueryConvertStrategy.ConvertConstantToComparedPropertyOrField,
parameter: group.Parameter, nullChecking: true);
//public static IEnumerable<TSource> Where<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate);
parentExpression = Expression.Call(typeof(Enumerable), "Where",
new Type[] { parent.GroupEnumerableType() },
parentExpression, whereExpression);
}
return(parentExpression);
}
private Expression CheckNullOnFirstGroup(ExpressionParserPieceGroup group, Expression currentExpression)
{
var path = string.Join(".", group.Pieces.Select(t => t.Name));
var whereExpression = QueryableHelpers.CreateConditionExpression(group.Parameter.Type, path,
ConditionOperators.NotEqual, null, QueryConvertStrategy.ConvertConstantToComparedPropertyOrField,
parameter: group.Parameter, nullChecking: true);
var whereBodyExpression = (whereExpression as LambdaExpression).Body;
whereBodyExpression = Expression.Not(whereBodyExpression);
var nullType = currentExpression.Type;
Expression ifTrueExpression = null;
if (QueryableHelpers.IsGenericEnumerable(nullType))
{
var listType = typeof(List <>).MakeGenericType(nullType.GenericTypeArguments.First());
ifTrueExpression = Expression.New(listType);
}
else
{
ifTrueExpression = Expression.Default(nullType);
}
return(Expression.Condition(whereBodyExpression, ifTrueExpression, currentExpression, currentExpression.Type));
}
protected Expression CompileGroup(ExpressionParserPieceGroup group, bool nullChecking)
{
var expr = group.Parameter as Expression;
group.Pieces.ForEach(piece =>
{
expr = Expression.PropertyOrField(expr, piece.Name);
});
return(expr);
}
