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/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DLinq / Dlinq / SqlClient / Query / TypeSource.cs / 1305376 / TypeSource.cs
using System; using System.Collections; using System.Collections.Generic; using System.Collections.ObjectModel; using System.Linq.Expressions; using System.Linq; using System.Reflection; using System.Data.Linq; using System.Data.Linq.Mapping; using System.Data.Linq.Provider; using System.Diagnostics.CodeAnalysis; namespace System.Data.Linq.SqlClient { ////// Method used for dealing with dynamic types. The ClrType of SqlNode is the /// statically known type originating in the source expression tree. For methods /// like GetType(), we need to know the dynamic type that will be constructed. /// internal static class TypeSource { private class Visitor : SqlVisitor { class UnwrapStack { public UnwrapStack(UnwrapStack last, bool unwrap) { Last = last; Unwrap = unwrap; } public UnwrapStack Last { get; private set; } public bool Unwrap { get; private set; } } UnwrapStack UnwrapSequences; internal SqlExpression sourceExpression; internal Type sourceType; [SuppressMessage("Microsoft.Maintainability", "CA1502:AvoidExcessiveComplexity", Justification="These issues are related to our use of if-then and case statements for node types, which adds to the complexity count however when reviewed they are easy to navigate and understand.")] internal override SqlNode Visit(SqlNode node) { if (node == null) return null; sourceExpression = node as SqlExpression; if (sourceExpression != null) { Type type = sourceExpression.ClrType; UnwrapStack unwrap = this.UnwrapSequences; while (unwrap != null) { if (unwrap.Unwrap) { type = TypeSystem.GetElementType(type); } unwrap = unwrap.Last; } sourceType = type; } if (sourceType != null && TypeSystem.GetNonNullableType(sourceType).IsValueType) { return node; // Value types can't also have a dynamic type. } if (sourceType != null && TypeSystem.HasIEnumerable(sourceType)) { return node; // Sequences can't be polymorphic. } switch (node.NodeType) { case SqlNodeType.ScalarSubSelect: case SqlNodeType.Multiset: case SqlNodeType.Element: case SqlNodeType.SearchedCase: case SqlNodeType.ClientCase: case SqlNodeType.SimpleCase: case SqlNodeType.Member: case SqlNodeType.DiscriminatedType: case SqlNodeType.New: case SqlNodeType.FunctionCall: case SqlNodeType.MethodCall: case SqlNodeType.Convert: // Object identity does not survive convert. It does survive Cast. // Dig no further. return node; case SqlNodeType.TypeCase: sourceType = ((SqlTypeCase)node).RowType.Type; return node; case SqlNodeType.Link: sourceType = ((SqlLink)node).RowType.Type; return node; case SqlNodeType.Table: sourceType = ((SqlTable)node).RowType.Type; return node; case SqlNodeType.Value: SqlValue val = (SqlValue)node; if (val.Value != null) { // In some cases the ClrType of a Value node may // differ from the actual runtime type of the value. // Therefore, we ensure here that the correct type is set. sourceType = val.Value.GetType(); } return node; } return base.Visit(node); } internal override SqlSelect VisitSelect(SqlSelect select) { /* * We're travelling throughof something like: * * SELECT * FROM * * Inside the expression there may be a reference to that * represents the dynamic type that we're trying to discover. * * In this case, the type relationship between AliasRef and Alias is * T to IEnumerable . * * We need to remember to 'unpivot' the type of IEnumerable to * get the correct dynamic type. * * Since SELECTs may be nested, we use a stack of pivots. * */ this.UnwrapSequences = new UnwrapStack(this.UnwrapSequences, true); VisitExpression(select.Selection); this.UnwrapSequences = this.UnwrapSequences.Last; return select; } internal override SqlExpression VisitAliasRef(SqlAliasRef aref) { if (this.UnwrapSequences != null && this.UnwrapSequences.Unwrap) { this.UnwrapSequences = new UnwrapStack(this.UnwrapSequences, false); this.VisitAlias(aref.Alias); this.UnwrapSequences = this.UnwrapSequences.Last; } else { this.VisitAlias(aref.Alias); } return aref; } internal override SqlExpression VisitColumnRef(SqlColumnRef cref) { this.VisitColumn(cref.Column); // Travel through column references return cref; } } /// /// Get a MetaType that represents the dynamic type of the given node. /// internal static MetaType GetSourceMetaType(SqlNode node, MetaModel model) { Visitor v = new Visitor(); v.Visit(node); Type type = v.sourceType; type = TypeSystem.GetNonNullableType(type); // Emulate CLR's behavior: strip nullability from type. return model.GetMetaType(type); } ////// Retrieve the expression that will represent the _dynamic_ type of the /// given expression. This is either a SqlDiscriminatedType or a SqlValue /// of type Type. /// internal static SqlExpression GetTypeSource(SqlExpression expr) { Visitor v = new Visitor(); v.Visit(expr); return v.sourceExpression; } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. All rights reserved.
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