/// <summary>
/// Modifies the given query model for fetching, adding an <see cref="AdditionalFromClause"/> and changing the <see cref="SelectClause.Selector"/> to
/// retrieve the result of the <see cref="AdditionalFromClause"/>.
/// For example, a fetch request such as <c>FetchMany (x => x.Orders)</c> will be transformed into a <see cref="AdditionalFromClause"/> selecting
/// <c>y.Orders</c> (where <c>y</c> is what the query model originally selected) and a <see cref="SelectClause"/> selecting the result of the
/// <see cref="AdditionalFromClause"/>.
/// This method is called by <see cref="FetchRequestBase.CreateFetchQueryModel"/> in the process of creating the new fetch query model.
/// </summary>
protected override void ModifyFetchQueryModel (QueryModel fetchQueryModel)
{
ArgumentUtility.CheckNotNull ("fetchQueryModel", fetchQueryModel);
var fromExpression = GetFetchedMemberExpression (new QuerySourceReferenceExpression (fetchQueryModel.MainFromClause));
var memberFromClause = new AdditionalFromClause (fetchQueryModel.GetNewName ("#fetch"), _relatedObjectType, fromExpression);
fetchQueryModel.BodyClauses.Add (memberFromClause);
var newSelector = new QuerySourceReferenceExpression (memberFromClause);
var newSelectClause = new SelectClause (newSelector);
fetchQueryModel.SelectClause = newSelectClause;
}
/// <summary>
/// Replaces the given parameter with a back-reference to the <see cref="IQuerySource"/> corresponding to <paramref name="referencedNode"/>.
/// </summary>
/// <param name="referencedNode">The referenced node.</param>
/// <param name="parameterToReplace">The parameter to replace with a <see cref="QuerySourceReferenceExpression"/>.</param>
/// <param name="expression">The expression in which to replace the parameter.</param>
/// <param name="context">The clause generation context.</param>
/// <returns><paramref name="expression"/>, with <paramref name="parameterToReplace"/> replaced with a <see cref="QuerySourceReferenceExpression"/>
/// pointing to the clause corresponding to <paramref name="referencedNode"/>.</returns>
public static Expression ReplaceParameterWithReference (
IQuerySourceExpressionNode referencedNode,
ParameterExpression parameterToReplace,
Expression expression,
ClauseGenerationContext context)
{
ArgumentUtility.CheckNotNull ("referencedNode", referencedNode);
ArgumentUtility.CheckNotNull ("parameterToReplace", parameterToReplace);
ArgumentUtility.CheckNotNull ("expression", expression);
ArgumentUtility.CheckNotNull ("context", context);
var clause = GetQuerySourceForNode (referencedNode, context);
var referenceExpression = new QuerySourceReferenceExpression (clause);
return ReplacingExpressionTreeVisitor.Replace (parameterToReplace, referenceExpression, expression);
}
protected override Expression VisitQuerySourceReferenceExpression (QuerySourceReferenceExpression expression)
{
ArgumentUtility.CheckNotNull ("expression", expression);
if (QuerySourceMapping.ContainsMapping (expression.ReferencedQuerySource))
{
return QuerySourceMapping.GetExpression (expression.ReferencedQuerySource);
}
else if (_throwOnUnmappedReferences)
{
var message = "Cannot replace reference to clause '" + expression.ReferencedQuerySource.ItemName + "', there is no mapped expression.";
throw new InvalidOperationException (message);
}
else
{
return expression;
}
}
protected override Expression VisitQuerySourceReferenceExpression (QuerySourceReferenceExpression expression)
{
ArgumentUtility.CheckNotNull ("expression", expression);
return Expression.Parameter (expression.Type, "[" + expression.ReferencedQuerySource.ItemName + "]");
}
protected override Expression VisitQuerySourceReferenceExpression (QuerySourceReferenceExpression expression)
{
ArgumentUtility.CheckNotNull ("expression", expression);
try
{
var accessorLambda = AccessorFindingExpressionTreeVisitor.FindAccessorLambda (expression, _itemExpression, _lambdaParameter);
return accessorLambda.Body;
}
catch (ArgumentException ex)
{
var message = string.Format (
"Cannot create a LambdaExpression that retrieves the value of '{0}' from items with a structure of '{1}'. The item expression does not "
+ "contain the value or it is too complex.",
FormattingExpressionTreeVisitor.Format (expression),
FormattingExpressionTreeVisitor.Format (_itemExpression));
throw new InvalidOperationException (message, ex);
}
}
