NHibernate custom criterion accent-insensitive.

gistfile1.cs

public class AccentInsensitiveLikeExpression : AbstractCriterion
  {
        private readonly string _propertyName;
      	private readonly object _value;
    		private readonly IProjection _projection;
    
    		public AccentInsensitiveLikeExpression(IProjection projection, string value, MatchMode matchMode)
    		{
    			_projection = projection;
    			_value = matchMode.ToMatchString(value);
    		}
    
    		public AccentInsensitiveLikeExpression(IProjection projection, object value)
    		{
    			_projection = projection;
    			_value = value;
    		}
    
    		public AccentInsensitiveLikeExpression(string propertyName, object value)
    		{
    			_propertyName = propertyName;
    			_value = value;
    		}
  
          public AccentInsensitiveLikeExpression(string propertyName, string value, MatchMode matchMode)
  			: this(propertyName, matchMode.ToMatchString(value))
  		  {
  		  }

        public override SqlString ToSqlString(ICriteria criteria, ICriteriaQuery criteriaQuery, IDictionary<string, IFilter> enabledFilters)
        {
            var columnNames = CriterionUtil.GetColumnNames(_propertyName, _projection, criteriaQuery, criteria, enabledFilters);
            var dialect = criteriaQuery.Factory.Dialect;

            if (columnNames.Length != 1)
            {
                throw new HibernateException("accent insensitive like may only be used with single-column properties");
            }

            var parameter = criteriaQuery.NewQueryParameter(GetParameterTypedValue(criteria, criteriaQuery)).Single();
            if (dialect is Oracle8iDialect)
                return GenerateOracleExpression(columnNames[0], dialect, parameter).ToSqlString();
            
            if (dialect is MsSql2000Dialect)
                return GenerateMsSqlExpression(columnNames[0], parameter).ToSqlString();

            throw new NotSupportedException();
        }

    		public override TypedValue[] GetTypedValues(ICriteria criteria, ICriteriaQuery criteriaQuery)
    		{
    			var typedValues = new List<TypedValue>();
    
    			if (_projection != null)
    			{
    				typedValues.AddRange(_projection.GetTypedValues(criteria, criteriaQuery));
    			}
    			typedValues.Add(GetParameterTypedValue(criteria, criteriaQuery));
    
    			return typedValues.ToArray();
    		}

    		public TypedValue GetParameterTypedValue(ICriteria criteria, ICriteriaQuery criteriaQuery)
    		{
    			var matchValue = _value.ToString().ToLower();
    			if (_projection != null)
    			{
    				return CriterionUtil.GetTypedValues(criteriaQuery, criteria, _projection, null, matchValue).Single();
    			}
    			return criteriaQuery.GetTypedValue(criteria, _propertyName, matchValue);
    		}
    
    		public override IProjection[] GetProjections()
    		{
    		    return _projection != null ? new[] { _projection } : null;
    		}
    
            public override string ToString()
    		{
    			return (_projection ?? (object)_propertyName) + " ilike " + _value;
    		}

        private SqlStringBuilder GenerateOracleExpression(SqlString columnName, Dialect dialect, Parameter parameter)
        {
            var sqlBuilder = new SqlStringBuilder();
            sqlBuilder.Add("translate")
                .Add("(")
                .Add(dialect.LowercaseFunction)
                .Add("(")
                .Add(columnName)
                .Add(")")
                .Add(",")
                .Add("'âàãáéêèíîòóôõüùúûçÿ'")
                .Add(",")
                .Add("'aaaaeeeiioooouuuucy'")
                .Add(")")
                .Add(" like ")
                .Add("translate")
                .Add("(")
                .Add(dialect.LowercaseFunction)
                .Add("(")
                .Add(parameter)
                .Add(")")
                .Add(",")
                .Add("'âàãáéêèíîòóôõüùúûçÿ'")
                .Add(",")
                .Add("'aaaaeeeiioooouuuucy'")
                .Add(")");

            return sqlBuilder;
        }

        private SqlStringBuilder GenerateMsSqlExpression(SqlString columnName, Parameter parameter)
        {
            var sqlBuilder = new SqlStringBuilder();
            sqlBuilder
                .Add(columnName)
                .Add(" like ")
                .Add(parameter)
                .Add(" collate latin1_general_ci_ai ");

            return sqlBuilder;
        }
    }