SqlBooleanizer.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DLinq / Dlinq / SqlClient / Query / SqlBooleanizer.cs / 1305376 / SqlBooleanizer.cs
                        
                        
                            using System.Data.Linq.Mapping; 


namespace System.Data.Linq.SqlClient {
 
    /// 
    /// Locate cases in which there is a 'Bit' but a 'Predicate' is expected or vice-versa. 
    /// Transform these expressions into expressions of the expected type. 
    /// 
    internal class SqlBooleanizer { 
        private class Booleanizer : SqlBooleanMismatchVisitor {
            private SqlFactory sql;

            internal Booleanizer(TypeSystemProvider typeProvider, MetaModel model) { 
                this.sql = new SqlFactory(typeProvider, model);
            } 
 
            internal override SqlSelect VisitSelect(SqlSelect select) {
                // DevDiv 179191 
                if (select.Where != null && select.Where.NodeType == SqlNodeType.Coalesce) {
                    SqlBinary bin = (SqlBinary)select.Where;
                    if (bin.Right.NodeType == SqlNodeType.Value) {
                        SqlValue value = (SqlValue)bin.Right; 
                        if (value.Value != null && value.Value.GetType() == typeof(bool) && (bool)value.Value == false) {
                            select.Where = bin.Left; 
                        } 
                    }
                } 

                return base.VisitSelect(select);
            }
 
            internal override SqlExpression ConvertValueToPredicate(SqlExpression valueExpression) {
                // Transform the 'Bit' expression into a 'Predicate' by forming the 
                // following operation: 
                //    OriginalExpr = 1
                // Yukon and later could also handle: 
                //    OriginalExpr = 'true'
                // but Sql2000 does not support this.
                return new SqlBinary(SqlNodeType.EQ,
                    valueExpression.ClrType, sql.TypeProvider.From(typeof(bool)), 
                    valueExpression,
                    sql.Value(typeof(bool), valueExpression.SqlType, true, false,  valueExpression.SourceExpression) 
                    ); 
            }
 
            internal override SqlExpression ConvertPredicateToValue(SqlExpression predicateExpression) {
                // Transform the 'Predicate' expression into a 'Bit' by forming the
                // following operation:
                //   CASE 
                //    WHEN predicateExpression THEN 1
                //    ELSE NOT(predicateExpression) THEN 0 
                //    ELSE NULL 
                //   END
 
                // Possible simplification to the generated SQL would be to detect when 'predicateExpression'
                // is SqlUnary(NOT) and use its operand with the literal 1 and 0 below swapped.
                SqlExpression valueTrue = sql.ValueFromObject(true, false, predicateExpression.SourceExpression);
                SqlExpression valueFalse = sql.ValueFromObject(false, false, predicateExpression.SourceExpression); 
                if (SqlExpressionNullability.CanBeNull(predicateExpression) != false) {
                    SqlExpression valueNull = sql.Value(valueTrue.ClrType, valueTrue.SqlType, null, false, predicateExpression.SourceExpression); 
                    return new SqlSearchedCase( 
                        predicateExpression.ClrType,
                        new SqlWhen[] { 
                            new SqlWhen(predicateExpression, valueTrue),
                            new SqlWhen(new SqlUnary(SqlNodeType.Not, predicateExpression.ClrType, predicateExpression.SqlType, predicateExpression, predicateExpression.SourceExpression), valueFalse)
                        },
                        valueNull, 
                        predicateExpression.SourceExpression
                        ); 
                } 
                else {
                    return new SqlSearchedCase( 
                        predicateExpression.ClrType,
                        new SqlWhen[] { new SqlWhen(predicateExpression, valueTrue) },
                        valueFalse,
                        predicateExpression.SourceExpression 
                        );
                } 
            } 
        }
 
        /// 
        /// Rationalize boolean expressions for the given node.
        /// 
        internal static SqlNode Rationalize(SqlNode node, TypeSystemProvider typeProvider, MetaModel model) { 
            return new Booleanizer(typeProvider, model).Visit(node);
        } 
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
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SqlBooleanizer.cs source code in C# .NET

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