expression studio 3 - Page 15

Enhanced Dynamic Filtering

- by Ricardo Peres

Remember my last post on dynamic filtering? Well, this time I'm extending the code in order to allow two levels of querying: Match type, represented by the following options: public enum MatchType { StartsWith = 0, Contains = 1 } And word match: public enum WordMatch { AnyWord = 0, AllWords = 1, ExactPhrase = 2 } You can combine the two levels in order to achieve the following combinations: MatchType.StartsWith + WordMatch.AnyWord Matches any record that starts with any of the words specified MatchType.StartsWith + WordMatch.AllWords Not available: does not make sense, throws an exception MatchType.StartsWith + WordMatch.ExactPhrase Matches any record that starts with the exact specified phrase MatchType.Contains + WordMatch.AnyWord Matches any record that contains any of the specified words MatchType.Contains + WordMatch.AllWords Matches any record that contains all of the specified words MatchType.Contains + WordMatch.ExactPhrase Matches any record that contains the exact specified phrase Here is the code: public static IList Search(IQueryable query, Type entityType, String dataTextField, String phrase, MatchType matchType, WordMatch wordMatch, Int32 maxCount) { String [] terms = phrase.Split(' ').Distinct().ToArray(); StringBuilder result = new StringBuilder(); PropertyInfo displayProperty = entityType.GetProperty(dataTextField); IList searchList = null; MethodInfo orderByMethod = typeof(Queryable).GetMethods(BindingFlags.Public | BindingFlags.Static).Where(m = m.Name == "OrderBy").ToArray() [ 0 ].MakeGenericMethod(entityType, displayProperty.PropertyType); MethodInfo takeMethod = typeof(Queryable).GetMethod("Take", BindingFlags.Public | BindingFlags.Static).MakeGenericMethod(entityType); MethodInfo whereMethod = typeof(Queryable).GetMethods(BindingFlags.Public | BindingFlags.Static).Where(m = m.Name == "Where").ToArray() [ 0 ].MakeGenericMethod(entityType); MethodInfo distinctMethod = typeof(Queryable).GetMethods(BindingFlags.Public | BindingFlags.Static).Where(m = m.Name == "Distinct" && m.GetParameters().Length == 1).Single().MakeGenericMethod(entityType); MethodInfo toListMethod = typeof(Enumerable).GetMethod("ToList", BindingFlags.Static | BindingFlags.Public).MakeGenericMethod(entityType); MethodInfo matchMethod = typeof(String).GetMethod ( (matchType == MatchType.StartsWith) ? "StartsWith" : "Contains", new Type [] { typeof(String) } ); MemberExpression member = Expression.MakeMemberAccess ( Expression.Parameter(entityType, "n"), displayProperty ); MethodCallExpression call = null; LambdaExpression where = null; LambdaExpression orderBy = Expression.Lambda ( member, member.Expression as ParameterExpression ); switch (matchType) { case MatchType.StartsWith: switch (wordMatch) { case WordMatch.AnyWord: call = Expression.Call ( member, matchMethod, Expression.Constant(terms [ 0 ]) ); where = Expression.Lambda ( call, member.Expression as ParameterExpression ); for (Int32 i = 1; i ()); where = Expression.Lambda ( Expression.Or ( where.Body, exp ), where.Parameters.ToArray() ); } break; case WordMatch.ExactPhrase: call = Expression.Call ( member, matchMethod, Expression.Constant(phrase) ); where = Expression.Lambda ( call, member.Expression as ParameterExpression ); break; case WordMatch.AllWords: throw (new Exception("The match type StartsWith is not supported with word match AllWords")); } break; case MatchType.Contains: switch (wordMatch) { case WordMatch.AnyWord: call = Expression.Call ( member, matchMethod, Expression.Constant(terms [ 0 ]) ); where = Expression.Lambda ( call, member.Expression as ParameterExpression ); for (Int32 i = 1; i ()); where = Expression.Lambda ( Expression.Or ( where.Body, exp ), where.Parameters.ToArray() ); } break; case WordMatch.ExactPhrase: call = Expression.Call ( member, matchMethod, Expression.Constant(phrase) ); where = Expression.Lambda ( call, member.Expression as ParameterExpression ); break; case WordMatch.AllWords: call = Expression.Call ( member, matchMethod, Expression.Constant(terms [ 0 ]) ); where = Expression.Lambda ( call, member.Expression as ParameterExpression ); for (Int32 i = 1; i ()); where = Expression.Lambda ( Expression.AndAlso ( where.Body, exp ), where.Parameters.ToArray() ); } break; } break; } query = orderByMethod.Invoke(null, new Object [] { query, orderBy }) as IQueryable; query = whereMethod.Invoke(null, new Object [] { query, where }) as IQueryable; if (maxCount != 0) { query = takeMethod.Invoke(null, new Object [] { query, maxCount }) as IQueryable; } searchList = toListMethod.Invoke(null, new Object [] { query }) as IList; return (searchList); } And this is how you'd use it: IQueryable query = ctx.MyEntities; IList list = Search(query, typeof(MyEntity), "Name", "Ricardo Peres", MatchType.Contains, WordMatch.ExactPhrase, 10 /*0 for all*/); SyntaxHighlighter.config.clipboardSwf = 'http://alexgorbatchev.com/pub/sh/2.0.320/scripts/clipboard.swf'; SyntaxHighlighter.brushes.CSharp.aliases = ['c#', 'c-sharp', 'csharp']; SyntaxHighlighter.all();

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