// Make this mess into multiply methods
// mistake to introduce classes search and comparator since they're not based on a interface
public List <Person> GetPersonsFromRepository(List <Tuple <Search, Comparator> > queries, PersonRepository repo)
{
var expressionTree = new List <Tuple <Expression, Comparator> >();
// this is the parameter like "person => person.Age = 10"
var parameterExpression = Expression.Parameter(typeof(Person), "person");
// Create each expression tree
foreach (var query in queries)
{
var search = query.Item1;
// Find parameter first (we already filtered this)
var parameterType =
typeof(Person).GetProperties()
.FirstOrDefault(
property => string.Equals(search.Property, property.Name, StringComparison.CurrentCultureIgnoreCase));
// https://msdn.microsoft.com/en-us/library/bb882637(v=vs.110).aspx
// Handle left hand (ex. "Name", "Age", "Birthday")
Expression left = Expression.Property(parameterExpression, parameterType);
Expression right = null;
// Handle right hand (ex. 10, "Patrick", '23-11-1993') and parse
// person => person.Age == 10
switch (parameterType.Name)
{
case "Name":
right = Expression.Constant(search.Condition, typeof(string));
break;
case "Birthday":
// TODO: Try and parse this earlier so we don't get an error
right = Expression.Constant(DateTime.Parse(search.Condition), typeof(DateTime));
break;
case "Age":
// TODO: Try and parse this earlier so we don't get an error
right = Expression.Constant(int.Parse(search.Condition), typeof(int));
break;
}
Expression expressionOperator = null;
// Handle operators
switch (search.Operator)
{
case '>':
expressionOperator = Expression.GreaterThan(left, right);
break;
case '<':
expressionOperator = Expression.LessThan(left, right);
break;
case '=':
expressionOperator = Expression.Equal(left, right);
break;
}
var comparator = query.Item2;
expressionTree.Add(new Tuple <Expression, Comparator>(expressionOperator, comparator));
}
var expressions = new List <Expression <Func <Person, bool> > >();
// If they're 'all null' then there's only one expression
if (expressionTree.All(tree => tree.Item2 == null))
{
expressions = expressionTree.Select(
expression => Expression.Lambda <Func <Person, bool> >(expression.Item1, parameterExpression)).ToList();
return(repo.GetPersons(expressions.FirstOrDefault().Compile()));
}
var expressionsTreesCombined = new List <Expression>();
for (int i = 0; i < expressionTree.Count; i++)
{
var pair = expressionTree[i];
var expression = pair.Item1;
var comparator = pair.Item2;
// if it's zero, it was the last comparator
if (comparator == null)
{
continue;
}
if (comparator?.Type == '&')
{
var nextExpression = expressionTree[i + 1].Item1;
expressionsTreesCombined.Add(Expression.And(expression, nextExpression));
}
else if (comparator?.Type == '|')
{
var nextExpression = expressionTree[i + 1].Item1;
expressionsTreesCombined.Add(Expression.Or(expression, nextExpression));
}
}
expressions = expressionsTreesCombined.Select(
expression => Expression.Lambda <Func <Person, bool> >(expression, parameterExpression)).ToList();
return(repo.GetPersons(expressions.FirstOrDefault().Compile()));
}
public Person GetPersonFromRepository(string searchProperty, char searchOperator, string searchCondition, PersonRepository repo)
{
var search = new Search(searchProperty, searchOperator, searchCondition);
var personTuple = new Tuple <Search, Comparator>(search, null);
var personParameter = new List <Tuple <Search, Comparator> >()
{
personTuple
};
return(GetPersonsFromRepository(personParameter, repo).FirstOrDefault());
}
