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/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DLinq / Dlinq / SqlClient / Query / SqlTypeConverter.cs / 1305376 / SqlTypeConverter.cs
using System; using System.Collections.Generic; using System.Text; using System.Data.Linq; using System.Diagnostics.CodeAnalysis; namespace System.Data.Linq.SqlClient { ////// The standard SQL text for a type conversion is CONVERT([newtype],value) /// Replace it with special SQL functions where necessary (e.g. char -> int uses UNICODE(value) instead). /// internal class SqlTypeConverter : SqlVisitor { protected SqlFactory sql; internal SqlTypeConverter(SqlFactory sql) { this.sql = sql; } bool StringConversionIsSafe(ProviderType oldSqlType, ProviderType newSqlType) { // if we are dealing with a conversion from a fixed-size string or char if (BothTypesAreStrings(oldSqlType, newSqlType)) { // we assume we can convert to an unknown size // we can do the conversion when both sizes are specified and the destination size is larger return !newSqlType.HasSizeOrIsLarge || OldWillFitInNew(oldSqlType, newSqlType); } // give the benefit of the doubt for conversion from non-string types return true; } bool StringConversionIsNeeded(ProviderType oldSqlType, ProviderType newSqlType) { if (BothTypesAreStrings(oldSqlType, newSqlType)) { bool stringsFixedSize = oldSqlType.IsFixedSize || newSqlType.IsFixedSize; if (!newSqlType.HasSizeOrIsLarge) { // we assume we can convert to an unknown size return true; } else if (OldWillFitInNew(oldSqlType, newSqlType)) { // we can do the conversion when both sizes are specified and the destination size is larger // but we only need to do it when one is fixed size return stringsFixedSize; } else { return false; } } else { return true; } } [SuppressMessage("Microsoft.Performance", "CA1822:MarkMembersAsStatic", Justification="Unknown reason.")] private bool OldWillFitInNew(ProviderType oldSqlType, ProviderType newSqlType) { bool result = newSqlType.IsLargeType // we can fit into a large type || !newSqlType.HasSizeOrIsLarge // if the type is not large, and doesn't have a size specified, assume OK || (!oldSqlType.IsLargeType // else, if the old type isn't large && oldSqlType.HasSizeOrIsLarge // and both old .. && newSqlType.HasSizeOrIsLarge // .. and new sizes are specified && newSqlType.Size >= oldSqlType.Size); // and if the new size is larger or equal to the old, then OK return result; } private bool BothTypesAreStrings(ProviderType oldSqlType, ProviderType newSqlType) { bool result = oldSqlType.IsSameTypeFamily(sql.TypeProvider.From(typeof(string))) && newSqlType.IsSameTypeFamily(sql.TypeProvider.From(typeof(string))); return result; } internal override SqlExpression VisitUnaryOperator(SqlUnary uo) { uo.Operand = this.VisitExpression(uo.Operand); if (uo.NodeType != SqlNodeType.Convert) { return uo; } ProviderType oldSqlType = uo.Operand.SqlType; ProviderType newSqlType = uo.SqlType; Type oldClrType = TypeSystem.GetNonNullableType(uo.Operand.ClrType); Type newClrType = TypeSystem.GetNonNullableType(uo.ClrType); if (newClrType == typeof(char)) { if (oldClrType == typeof(bool)) { throw Error.ConvertToCharFromBoolNotSupported(); } if (oldSqlType.IsNumeric) { // numeric --> char return sql.FunctionCall(uo.ClrType, "NCHAR", new SqlExpression[] { uo.Operand }, uo.SourceExpression); } if (StringConversionIsSafe(oldSqlType, newSqlType)) { if (StringConversionIsNeeded(oldSqlType, newSqlType)) { // set the new size to the (potentially smaller) oldSqlType.Size uo.SetSqlType(sql.TypeProvider.From(uo.ClrType, oldSqlType.HasSizeOrIsLarge ? oldSqlType.Size : (int?)null)); } } else { throw Error.UnsafeStringConversion(oldSqlType.ToQueryString(), newSqlType.ToQueryString()); } } else if (oldClrType == typeof(char) && (oldSqlType.IsChar || oldSqlType.IsString) && newSqlType.IsNumeric) { // char --> int return sql.FunctionCall(newClrType, sql.TypeProvider.From(typeof(int)), "UNICODE", new SqlExpression[] { uo.Operand }, uo.SourceExpression); } else if (newClrType == typeof(string)) { if (oldClrType == typeof(double)) { // use longer format if it was a double in the CLR expression return ConvertDoubleToString(uo.Operand, uo.ClrType); } else if (oldClrType == typeof(bool)) { // use 'true' or 'false' if it was a bool in the CLR expression return ConvertBitToString(uo.Operand, uo.ClrType); } else if (StringConversionIsSafe(oldSqlType, newSqlType)) { if (StringConversionIsNeeded(oldSqlType, newSqlType)) { // set the new size to the (potentially smaller) oldSqlType.Size uo.SetSqlType(sql.TypeProvider.From(uo.ClrType, oldSqlType.HasSizeOrIsLarge ? oldSqlType.Size : (int?)null)); } } else { throw Error.UnsafeStringConversion(oldSqlType.ToQueryString(), newSqlType.ToQueryString()); } } return uo; } private SqlExpression ConvertDoubleToString(SqlExpression expr, Type resultClrType) { // for double we need the form CONVERT(NVARCHAR(30),...,2) to get the full precision // fake up a SqlExpression for NVARCHAR(30) SqlExpression nvarchar = sql.FunctionCall( typeof(void), "NVARCHAR", new SqlExpression[] { sql.ValueFromObject(30, false, expr.SourceExpression) }, expr.SourceExpression ); return sql.FunctionCall( resultClrType, "CONVERT", new SqlExpression[] { nvarchar, expr, sql.ValueFromObject(2, false, expr.SourceExpression) }, expr.SourceExpression ); } private SqlExpression ConvertBitToString(SqlExpression expr, Type resultClrType) { return new SqlSearchedCase( resultClrType, new SqlWhen[] { new SqlWhen(expr, sql.ValueFromObject(true.ToString(), false, expr.SourceExpression)) }, sql.ValueFromObject(false.ToString(), false, expr.SourceExpression), expr.SourceExpression ); } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. 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