示例#1
0
            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));
            }