如何转换数据表中ASP.NET/C#到词典 [英] How to convert datatable to dictionary in ASP.NET/C#

问题描述

的数据表如下：

ClassID  ClassName  StudentID  StudentName
    1        A          1000      student666
    2        B          1100      student111
    5        C          1500      student777
    1        A          1200      student222
    2        B          1080      student999

字典键由的ClassID，类名和值是由StudentID，StudentName的。

The dictionary key is composed of "ClassID ,ClassName " and value is composed of "StudentID,StudentName" .

Dictionary<string, string> d = new Dictionary<string, string>();

foreach (DataRow dr in table.Rows)
{
    string key=dr["ClassID"].ToString() + dr["ClassName"].ToString();
    if (!d.ContainsKey(key))
    {
        //Do something();......
    }
    else
    {
        //Do something();......
    }
}
foreach (var s in d.Keys)
{
    Response.Write(s+"|+"+d[s]+"<br>");
}

有一个更快的方法？

Is there a faster way?

假定键'1，A'，值应该是'1000，student666'和'1200，student222

assume that key is '1,A' ,Value should be ' 1000,student666' and '1200,student222'

推荐答案

下面去即可。使用LINQ，你可以将它们分组，然后，如果你想进行字符串连接。

Here goes then. Using Linq, you can group them then perform string concatenation if you want.

// Start by grouping
var groups = table.AsEnumerable()
        .Select(r => new {
                      ClassID = r.Field<int>("ClassID"),
                      ClassName = r.Field<string>("ClassName"),
                      StudentID = r.Field<int>("StudentID"),
                      StudentName = r.Field<string>("StudentName")
                  }).GroupBy(e => new { e.ClassID, e.ClassName });

// Then create the strings. The groups will be an IGrouping<TGroup, T> of anonymous objects but
// intellisense will help you with that.
foreach(var line in groups.Select(g => String.Format("{0},{1}|+{2}<br/>", 
                                       g.Key.ClassID, 
                                       g.Key.ClassName,
                                       String.Join(" and ", g.Select(e => String.Format("{0},{1}", e.StudentID, e.StudentName))))))
{
    Response.Write(line);
}

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