public static IQueryable AppendWhere(IQueryable src, CriteriaOperator op)
{
var converter = new CriteriaToExpressionConverter();
if (object.ReferenceEquals((object)op, (object)null))
{
return(src);
}
ParameterExpression thisExpression = Expression.Parameter(src.ElementType, "");
Expression expression =
Expression.Quote(Expression.Lambda(converter.Convert(thisExpression, op),
new ParameterExpression[1] {
thisExpression
}));
MethodCallExpression methodCallExpression =
Expression.Call(typeof(Queryable), "Where",
new Type[1] {
src.ElementType
}, new Expression[2]
{
src.Expression, expression
});
return(src.Provider.CreateQuery(methodCallExpression));
}
protected override Expression VisitMethodCall(MethodCallExpression node)
{
if (node.Method.Name == "Where")
{
var converter = new CriteriaToExpressionConverter();
var elementType = node.Method.ReturnType.GetGenericArguments()[0];
ParameterExpression thisExpression = Expression.Parameter(elementType);
var criteria = DataServiceQueryCriteriaVisitor.Prepare(_filter);
if (criteria is FunctionOperator && criteria.ToString().Contains("IsPriorDays"))
{
var priorDays = (FunctionOperator)criteria;
BinaryOperator prirOperator = new BinaryOperator();
prirOperator.LeftOperand = priorDays.Operands[1];
int timeSpan = int.Parse(priorDays.Operands[2].ToString()) * (-1);
prirOperator.RightOperand = new ConstantValue(DateTime.Now.AddDays(timeSpan));
prirOperator.OperatorType = BinaryOperatorType.Less;
criteria = prirOperator;
}
else if (criteria is GroupOperator && criteria.ToString().Contains("IsPriorDays"))
{
var groupOperator = (GroupOperator)criteria;
var priorDays = (FunctionOperator)groupOperator.Operands[0];
BinaryOperator prirOperator = new BinaryOperator();
prirOperator.LeftOperand = priorDays.Operands[1];
int timeSpan = int.Parse(priorDays.Operands[2].ToString()) * (-1);
prirOperator.RightOperand = new ConstantValue(DateTime.Now.AddDays(timeSpan));
prirOperator.OperatorType = BinaryOperatorType.Less;
criteria = prirOperator;
}
var expression = Expression.Lambda(converter.Convert(thisExpression, criteria), thisExpression);
Expression filterExpression = Expression.Quote(expression);
return(Expression.Call(node.Method, node, filterExpression));
}
return(base.VisitMethodCall(node));
}
public Expression Convert(ParameterExpression thisExpression, DevExpress.Data.Filtering.CriteriaOperator op)
{
var converter = new CriteriaToExpressionConverter();
Expression expression = converter.Convert(thisExpression, op);
var visitor = new NullPropagationEraseViistor();
return(visitor.Visit(expression));
}