如何联接不同文件的内容 (LINQ) (C#)

项目
2022/09/22

本示例演示如何联接两个逗号分隔文件中的数据，这两个文件共享一个用作匹配键的公共值。如果需要合并来自两个电子表格的数据，或者从一个电子表格和具有另一种格式的文件合并到一个新文件时，此技术很有用。可以修改此示例以用于任何类型的结构化文本。

创建数据文件

将以下行复制到名为 scores.csv 的文件，并将文件保存到项目文件夹。此文件表示电子表格数据。第 1 列是学生的 ID，第 2 至 5 列是测验分数。

csv

111, 97, 92, 81, 60  
112, 75, 84, 91, 39  
113, 88, 94, 65, 91  
114, 97, 89, 85, 82  
115, 35, 72, 91, 70  
116, 99, 86, 90, 94  
117, 93, 92, 80, 87  
118, 92, 90, 83, 78  
119, 68, 79, 88, 92  
120, 99, 82, 81, 79  
121, 96, 85, 91, 60  
122, 94, 92, 91, 91

将以下行复制到名为 names.csv 的文件，并将文件保存到项目文件夹。此文件表示电子表格，其中包含学生的姓氏、名字和学生 ID。

csv

Omelchenko,Svetlana,111  
O'Donnell,Claire,112  
Mortensen,Sven,113  
Garcia,Cesar,114  
Garcia,Debra,115  
Fakhouri,Fadi,116  
Feng,Hanying,117  
Garcia,Hugo,118  
Tucker,Lance,119  
Adams,Terry,120  
Zabokritski,Eugene,121  
Tucker,Michael,122

示例

using System;
using System.Collections.Generic;
using System.Linq;

class JoinStrings  
{  
    static void Main()  
    {  
        // Join content from dissimilar files that contain  
        // related information. File names.csv contains the student  
        // name plus an ID number. File scores.csv contains the ID
        // and a set of four test scores. The following query joins  
        // the scores to the student names by using ID as a  
        // matching key.  
  
        string[] names = System.IO.File.ReadAllLines(@"../../../names.csv");  
        string[] scores = System.IO.File.ReadAllLines(@"../../../scores.csv");  
  
        // Name:    Last[0],       First[1],  ID[2]  
        //          Omelchenko,    Svetlana,  11  
        // Score:   StudentID[0],  Exam1[1]   Exam2[2],  Exam3[3],  Exam4[4]  
        //          111,           97,        92,        81,        60  
  
        // This query joins two dissimilar spreadsheets based on common ID value.  
        // Multiple from clauses are used instead of a join clause  
        // in order to store results of id.Split.  
        IEnumerable<string> scoreQuery1 =  
            from name in names  
            let nameFields = name.Split(',')  
            from id in scores  
            let scoreFields = id.Split(',')  
            where Convert.ToInt32(nameFields[2]) == Convert.ToInt32(scoreFields[0])
            select nameFields[0] + "," + scoreFields[1] + "," + scoreFields[2]
                   + "," + scoreFields[3] + "," + scoreFields[4];  
  
        // Pass a query variable to a method and execute it  
        // in the method. The query itself is unchanged.  
        OutputQueryResults(scoreQuery1, "Merge two spreadsheets:");  
  
        // Keep console window open in debug mode.  
        Console.WriteLine("Press any key to exit");  
        Console.ReadKey();  
    }  
  
    static void OutputQueryResults(IEnumerable<string> query, string message)  
    {  
        Console.WriteLine(System.Environment.NewLine + message);  
        foreach (string item in query)  
        {  
            Console.WriteLine(item);  
        }  
        Console.WriteLine("{0} total names in list", query.Count());  
    }  
}  
/* Output:  
Merge two spreadsheets:
Omelchenko, 97, 92, 81, 60
O'Donnell, 75, 84, 91, 39
Mortensen, 88, 94, 65, 91
Garcia, 97, 89, 85, 82
Garcia, 35, 72, 91, 70
Fakhouri, 99, 86, 90, 94
Feng, 93, 92, 80, 87
Garcia, 92, 90, 83, 78
Tucker, 68, 79, 88, 92
Adams, 99, 82, 81, 79
Zabokritski, 96, 85, 91, 60
Tucker, 94, 92, 91, 91
12 total names in list
 */

如何联接不同文件的内容 (LINQ) (C#)

创建数据文件

示例

另请参阅