DataTable中的C＃组DataRows

Question

I have a DataTable with two columns: File & Email

C://file1.jpg aaa@gmail.com  
C://file2.jpg aaa@gmail.com  
C://file3.jpg bbb@gmail.com  
C://file4.jpg ccc@gmail.com  
C://file5.jpg bbb@gmail.com

In my code i loop through the DataRow s and send an email to Email with File attached.

Problem:

I need to somehow check if there are any other DataRow s with the same Email and if so, send just one email with multiple attachments.

So the above DataTable would result in 3 emails:

file1,file2 sent to aaa@gmail.com  
file3,file5 sent to bbb@gmail.com  
file4 sent to ccc@gmail.com

My code sample:

foreach (DataRow row in dt.Rows) {
     string file = row[0].ToString();
     string email = row[1].ToString();
     SendEmailWithAttachments(email,file);
}

I could pass a StringCollection or an array to my SendEmailWithAttachments() function then loop throught it and attach all the files, but how do I group these DataRow s in first place

Answer 1

Using the GroupBy Linq extension you could handle your DataRows grouping them for the Email field, then foreach create a list of strings with the file names.

Of course, you need also to change the SendMailWithAttachments to receive as second parameter a List<string> instead of a single string

var g = dt.AsEnumerable().GroupBy(d => d.Field<string>("Email"));
foreach (var x in g)
{
    List<string> files = new List<string>();
    foreach (var z in x)
        files.Add(z.Field<string>("File"));

    SendEmailWithAttachments(email,files);

}

Answer 2

You could use GroupBy to group by email:

        DataTable dt = new DataTable();
        dt.Columns.Add("Path");
        dt.Columns.Add("Email");
        DataRow dr = dt.NewRow();
        dr.ItemArray=new object[2]{"C://file1.jpg", "aaa@gmail.com"};
        dt.Rows.Add(dr);
        dr = dt.NewRow();

        dr.ItemArray=new object[2]{"C://file2.jpg", "aaa@gmail.com"};
        dt.Rows.Add(dr);
        dr = dt.NewRow();
        dr.ItemArray=new object[2]{"C://file3.jpg", "bbb@gmail.com"};
        dt.Rows.Add(dr);
        dr = dt.NewRow();
        dr.ItemArray=new object[2]{"C://file4.jpg", "ccc@gmail.com"};
        dt.Rows.Add(dr);
        dr = dt.NewRow();
        dr.ItemArray=new object[2]{"C://file5.jpg", "bbb@gmail.com"};
        dt.Rows.Add(dr);


        var grouped=dt.AsEnumerable().GroupBy(x=>x.Field<string>("Email"));

        foreach (var mail in grouped)
        {
            List<string> filesForEmail = new List<string>();
            foreach (var file in mail)
            {
                filesForEmail.Add(file.Field<string>("Path"));
            }

            SendEmailWithAttachments(mail.Key, filesForEmail);
        }