// Executes the expression tree that is passed to it.
internal static object Execute(Expression expression, bool IsEnumerable)
{
// The expression must represent a query over the data source.
if (!IsQueryOverDataSource(expression))
{
throw new InvalidProgramException("No query over the data source was specified.");
}
// Find the call to Where() and get the lambda expression predicate.
InnermostWhereFinder whereFinder = new InnermostWhereFinder();
MethodCallExpression whereExpression = whereFinder.GetInnermostWhere(expression);
LambdaExpression lambdaExpression = (LambdaExpression)((UnaryExpression)(whereExpression.Arguments[1])).Operand;
// Send the lambda expression through the partial evaluator.
lambdaExpression = (LambdaExpression)Evaluator.PartialEval(lambdaExpression);
// Get the place name(s) to query the Web service with.
LocationFinder lf = new LocationFinder(lambdaExpression.Body);
List <string> locations = lf.Locations;
if (locations.Count == 0)
{
throw new InvalidQueryException("You must specify at least one place name in your query.");
}
// Call the Web service and get the results.
Place[] places = WebServiceHelper.GetPlacesFromTerraServer(locations);
// Copy the IEnumerable places to an IQueryable.
IQueryable <Place> queryablePlaces = places.AsQueryable <Place>();
// Copy the expression tree that was passed in, changing only the first
// argument of the innermost MethodCallExpression.
ExpressionTreeModifier treeCopier = new ExpressionTreeModifier(queryablePlaces);
Expression newExpressionTree = treeCopier.Visit(expression);
// This step creates an IQueryable that executes by replacing Queryable methods with Enumerable methods.
if (IsEnumerable)
{
return(queryablePlaces.Provider.CreateQuery(newExpressionTree));
}
else
{
return(queryablePlaces.Provider.Execute(newExpressionTree));
}
}
// Executes the expression tree that is passed to it.
internal static object Execute(Expression expression, bool IsEnumerable)
{
// The expression must represent a query over the data source.
if (!IsQueryOverDataSource(expression))
throw new InvalidProgramException("No query over the data source was specified.");
// Find the call to Where() and get the lambda expression predicate.
InnermostWhereFinder whereFinder = new InnermostWhereFinder();
MethodCallExpression whereExpression = whereFinder.GetInnermostWhere(expression);
LambdaExpression lambdaExpression = (LambdaExpression)((UnaryExpression)(whereExpression.Arguments[1])).Operand;
// Send the lambda expression through the partial evaluator.
lambdaExpression = (LambdaExpression)Evaluator.PartialEval(lambdaExpression);
// Get the place name(s) to query the Web service with.
LocationFinder lf = new LocationFinder(lambdaExpression.Body);
List<string> locations = lf.Locations;
if (locations.Count == 0)
throw new InvalidQueryException("You must specify at least one place name in your query.");
// Call the Web service and get the results.
Place[] places = WebServiceHelper.GetPlacesFromTerraServer(locations);
// Copy the IEnumerable places to an IQueryable.
IQueryable<Place> queryablePlaces = places.AsQueryable<Place>();
// Copy the expression tree that was passed in, changing only the first
// argument of the innermost MethodCallExpression.
ExpressionTreeModifier treeCopier = new ExpressionTreeModifier(queryablePlaces);
Expression newExpressionTree = treeCopier.Visit(expression);
// This step creates an IQueryable that executes by replacing Queryable methods with Enumerable methods.
if (IsEnumerable)
return queryablePlaces.Provider.CreateQuery(newExpressionTree);
else
return queryablePlaces.Provider.Execute(newExpressionTree);
}
