/// <summary>
/// Creates a lambda expression, that checks a Document to satisfy the list of conditions.
/// Then compiles it and returns a predicate.
/// </summary>
private static Func <Document, bool> CreatePredicate(SearchConditions conditions, Type entityType)
{
// parameter, that represents input Document
var docParameter = Expression.Parameter(typeof(Document));
Expression predicateExp = null;
foreach (var condition in conditions.Flatten())
{
string fieldName = condition.Item1;
var fieldPropertyInfo = entityType.GetProperty(fieldName);
if (fieldPropertyInfo == null)
{
throw new InvalidOperationException(string.Format("An entity type {0} doesn't contain a property with name {1}, which was specified in search condition", entityType.Name, fieldName));
}
var fieldType = fieldPropertyInfo.PropertyType;
var fieldValues = condition.Item2.Values;
// operation of getting a Document property value by it's name
Expression getFieldExp = Expression.Property(docParameter, "Item", Expression.Constant(fieldName));
if (fieldType.BaseType == typeof(Enum))
{
// need to convert enums to ints
getFieldExp = Expression.Convert(getFieldExp, typeof(int));
}
// operation of converting the property to fieldType
var operand1 = Expression.Convert(getFieldExp, fieldType);
Expression conditionExp;
if (condition.Item2.Operator == ScanOperator.In)
{
// special support for IN operator
var valueList = new ArrayList();
foreach (var fieldValue in fieldValues)
{
valueList.Add(fieldValue.ToObject(fieldType));
}
conditionExp = Expression.Call
(
Expression.Constant(valueList),
"Contains",
new Type[0],
Expression.Convert(operand1, typeof(object))
);
}
else
{
Expression valueExp = Expression.Constant(fieldValues[0]);
if (fieldType.BaseType == typeof(Enum))
{
// need to convert enums to ints
valueExp = Expression.Convert(valueExp, typeof(int));
}
// operation of converting the fieldValue to fieldType
var operand2 = Expression.Convert(valueExp, fieldType);
// now getting a predicate for current field
conditionExp = ScanOperatorToExpression(condition.Item2.Operator, operand1, operand2);
}
// attaching it to other predicates
predicateExp = predicateExp == null ? conditionExp : Expression.AndAlso(predicateExp, conditionExp);
}
Debug.Assert(predicateExp != null);
// compiling the lambda into a predicate
return((Func <Document, bool>)Expression.Lambda(predicateExp, docParameter).Compile());
}
/// <summary>
/// Creates a lambda expression, that checks a Document to satisfy the list of conditions.
/// Then compiles it and returns a predicate.
/// </summary>
private static Func<Document, bool> CreatePredicate(SearchConditions conditions, Type entityType)
{
// parameter, that represents input Document
var docParameter = Expression.Parameter(typeof(Document));
Expression predicateExp = null;
foreach (var condition in conditions.Flatten())
{
string fieldName = condition.Item1;
var fieldPropertyInfo = entityType.GetProperty(fieldName);
if (fieldPropertyInfo == null)
{
throw new InvalidOperationException(string.Format("An entity type {0} doesn't contain a property with name {1}, which was specified in search condition", entityType.Name, fieldName));
}
var fieldType = fieldPropertyInfo.PropertyType;
var fieldValues = condition.Item2.Values;
// operation of getting a Document property value by it's name
Expression getFieldExp = Expression.Property(docParameter, "Item", Expression.Constant(fieldName));
if (fieldType.BaseType == typeof (Enum))
{
// need to convert enums to ints
getFieldExp = Expression.Convert(getFieldExp, typeof (int));
}
// operation of converting the property to fieldType
var operand1 = Expression.Convert(getFieldExp, fieldType);
Expression conditionExp;
if (condition.Item2.Operator == ScanOperator.In)
{
// special support for IN operator
var valueList = new ArrayList();
foreach (var fieldValue in fieldValues)
{
valueList.Add(fieldValue.ToObject(fieldType));
}
conditionExp = Expression.Call
(
Expression.Constant(valueList),
"Contains",
new Type[0],
Expression.Convert(operand1, typeof(object))
);
}
else
{
Expression valueExp = Expression.Constant(fieldValues[0]);
if (fieldType.BaseType == typeof(Enum))
{
// need to convert enums to ints
valueExp = Expression.Convert(valueExp, typeof(int));
}
// operation of converting the fieldValue to fieldType
var operand2 = Expression.Convert(valueExp, fieldType);
// now getting a predicate for current field
conditionExp = ScanOperatorToExpression(condition.Item2.Operator, operand1, operand2);
}
// attaching it to other predicates
predicateExp = predicateExp == null ? conditionExp : Expression.AndAlso(predicateExp, conditionExp);
}
Debug.Assert(predicateExp != null);
// compiling the lambda into a predicate
return (Func<Document, bool>)Expression.Lambda( predicateExp, docParameter ).Compile();
}