Question

假设我有一个这样的课程：

class Person
{
   string FirstName;
   string MiddleName;
   string LastName;
}

假设我有这样的样本数据：

William Henry  Gates
Steven  Paul   Jobs 
Mark    Elliot Zuckerberg

然后，在Entity Framework / Linq中，我可以进行如下搜索：

string search = "paul";

search = search.ToUpper();
var people = db.People
    .Where(p => p.FirstName.ToUpper().Contains(search)
    .Where(p => p.MiddleName.ToUpper().Contains(search)
    .Where(p => p.LastName.ToUpper().Contains(search);

这很有效。但是，如果用户搜索，例如：

search = "Henry Gates";

糟糕..理论上，（1）必须有效：

    .Where(p => (p.FirstName +" "+ p.MiddleName +" "+ p.LastName).ToUpper().Contains(search);

或（2）必须有效：

    .Where(p => (p.FirstName.ToUpper() +" "+ p.MiddleName.ToUpper() +" "+ p.LastName.ToUpper()).Contains(search);

并且有一个选项（3）我能想到：

.Select(p => new {FullName = p.FirstName +" "+ p.MiddleName +" "+ p.LastName)} )
.Where(p => p.FullName.Contains(search) )

最后，我的问题。在小表中，这不是那么相关，但在大表（如500k记录）中，它可能是一个问题，因为（在我的示例中）FirstName，MiddleName和LastName是索引字段，并且在每个字段中单独搜索很好，但是连接查询中的字段，SQL将执行全表扫描而不是使用索引，这使得简单的查询变得非常缓慢。

使用EntityFramework / Linq更复杂，因为我不确切知道将用于连接我的字段的标准是什么。

那么在连续列中搜索的方式是什么？

感谢您的帮助

Answer 1

如果位置不相关，您可以先将输入字符串分解为List，然后使用contains查找匹配结果

// Define the search string
List<string> searchInput = new List<string> { "Paul", "Henry Gates", "Gates Henry" };

// Define the data
List<Person> persons = new List<Person>();
persons.Add(new Person() { FirstName = "William", MiddleName = "Henry", LastName = "Gates" });
persons.Add(new Person() { FirstName = "Steven", MiddleName = "Paul", LastName = "Jobs" });
persons.Add(new Person() { FirstName = "Mark", MiddleName = "Elliot", LastName = "Zuckerberg" });

// It may problem if you want to specific the field in sequence
persons.Add(new Person() { FirstName = "Henry", MiddleName = "Elliot", LastName = "Gates" });
// Another problem if a field contains all values
persons.Add(new Person() { FirstName = "Henry Gates", MiddleName = "Elliot", LastName = "Gates" });

// find the person
foreach (string input in searchInput)
{
    List<string> inputList = input.Split(' ').Select(s => s.ToUpperInvariant()).ToList();
    var qry = persons.Where(p => inputList.Contains(p.FirstName.ToUpperInvariant()) ||
                                    inputList.Contains(p.MiddleName.ToUpperInvariant()) ||
                                    inputList.Contains(p.LastName.ToUpperInvariant()));
    var results = qry.ToList();
    Console.WriteLine(string.Format("Search: {0} Found: {1}", input, results.Count));
    foreach(var p in results)
    {
        Console.WriteLine(p.ToString());
    }
    Console.WriteLine();
}

结果如下：

Search: Paul Found: 1
First Name: Steven; Middle Name: Paul; Last Name: Jobs

Search: Henry Gates Found: 3
First Name: William; Middle Name: Henry; Last Name: Gates
First Name: Henry; Middle Name: Elliot; Last Name: Gates
First Name: Henry Gates; Middle Name: Elliot; Last Name: Gates

Search: Gates Henry Found: 3
First Name: William; Middle Name: Henry; Last Name: Gates
First Name: Henry; Middle Name: Elliot; Last Name: Gates
First Name: Henry Gates; Middle Name: Elliot; Last Name: Gates

希望这符合您的目的

小提琴：http://rextester.com/XFXBEQ27713

在连接列中搜索的方法是什么？

1 个答案: