private static Func <TFrom, TTo> CreateConversion <TFrom, TTo>(
IKeyInfo <TFrom> fromKeyInfo,
IKeyInfo <TTo> toKeyInfo,
int[] mapping)
{
IKeyInfoHelper from = GetKeyInfoHelper(fromKeyInfo);
IKeyInfoHelper to = GetKeyInfoHelper(toKeyInfo);
ParameterExpression keyParam = Expression.Parameter(fromKeyInfo.KeyType);
Expression body =
KeyExpressionHelper.CreateKeyConversionExpression(
keyParam,
toKeyInfo.EntityKeyMembers,
mapping,
from,
to);
return(Expression.Lambda <Func <TFrom, TTo> >(body, keyParam).Compile());
}
protected override Expression VisitMethodCall(MethodCallExpression node)
{
if (!node.Method.IsGenericMethod ||
node.Method.GetGenericMethodDefinition() != this.Original)
{
// Not GroupJoin
return(base.VisitMethodCall(node));
}
ConstantExpression secondExpression = node.Arguments[1] as ConstantExpression;
if (secondExpression == null)
{
// Not constant expression
return(base.VisitMethodCall(node));
}
ITable table = secondExpression.Value as ITable;
if (table == null)
{
// Not table
return(base.VisitMethodCall(node));
}
LambdaExpression secondKeySelector =
ExpressionHelper.SkipQuoteNode(node.Arguments[3]) as LambdaExpression;
Type keyType = secondKeySelector.Body.Type;
IKeyInfoHelper helper = this.GetKeyInfoHelper(keyType);
if (helper == null)
{
// Cannot detect key type
return(base.VisitMethodCall(node));
}
// Try to parse expression
MemberInfo[] keyMembers;
if (!helper.TryParseKeySelectorExpression(
secondKeySelector.Body,
false,
out keyMembers))
{
// Cannot parse key
return(base.VisitMethodCall(node));
}
IIndex matchedIndex = null;
int[] mapping = null;
foreach (IIndex index in table.Indexes)
{
if (KeyExpressionHelper.TryGetMemberMapping(
index.KeyInfo.EntityKeyMembers,
keyMembers,
out mapping))
{
matchedIndex = index;
break;
}
}
if (matchedIndex == null)
{
// No matched index was found
return(base.VisitMethodCall(node));
}
var indexServices = GetKeyInfoHelper(matchedIndex.KeyInfo);
if (indexServices == null)
{
return(base.VisitMethodCall(node));
}
// Create key converter
ParameterExpression keyConverterParam = Expression.Parameter(keyType, "x");
LambdaExpression keyConverter =
Expression.Lambda(
KeyExpressionHelper.CreateKeyConversionExpression(keyConverterParam, matchedIndex.KeyInfo.EntityKeyMembers, mapping, helper, indexServices),
keyConverterParam);
// Create key emptyness detector
ParameterExpression keyEmptinessDetectorParam = Expression.Parameter(keyType, "x");
LambdaExpression keyEmptinessDetector =
Expression.Lambda(
KeyExpressionHelper.CreateKeyEmptinessDetector(
keyEmptinessDetectorParam,
helper),
keyEmptinessDetectorParam);
Type[] generics = node.Method.GetGenericArguments();
// GroupJoinIndexed call
MethodInfo indexedMethod = this.Indexed
.MakeGenericMethod(
generics[0],
generics[1],
generics[2],
matchedIndex.KeyInfo.KeyType,
generics[3]);
Expression indexedCall =
Expression.Call(
node.Object,
indexedMethod,
this.Visit(node.Arguments[0]),
Expression.Constant(matchedIndex),
ExpressionHelper.SkipQuoteNode(node.Arguments[2]),
keyEmptinessDetector,
keyConverter,
ExpressionHelper.SkipQuoteNode(node.Arguments[4]));
Type elementType = ReflectionHelper.GetElementType(indexedCall.Type);
// AsQueryable call
return(Expression.Call(
null,
QueryMethods.AsQueryable.MakeGenericMethod(elementType),
indexedCall));
}