DataTable group by and iterate through C#

Question

I have a datatable which was returned from database.

the content is similar below:

UserId | Address | Phone
 1        blah     0123
 1        blah2    3445
 2        sdsdf    2343
 2        ssf      2223
 3        sadss    2321

This is the content of DataTable which is returned from database.

Now I just would like to group the results by User Id and loop through to out put result

foreach (DataRow userRow in DataTableGroupedByUser){

foreach (DataRow restOfColumns in AddressAndPhoneRows){

Output user details } }

The output I would get should be:

User Id: 1

Address   Phone
1- blah   0123
2- blah2  3445

User Id 2:
  Address   Phone
1- sdsdf    2343
2- ssf      2223

user Id :3 ...

I hope you get the idea.

Basically I do not want to query the database many times for each user but just use one query to pull all data and handle the grouping in the memory.

There are also other reason for this.

Is there any way to achieve this by using DataTable and filtering?

Answer 1

You can use LINQ:

var groupedByUserId = table.AsEnumerable().GroupBy(row => row.Field<int>("UserId"));

foreach(var group in groupedByUserId)
{
    Console.WriteLine("User Id: {0}", group.Key);
    Console.WriteLine("Address   Phone");
    int rowNum = 0;
    foreach(DataRow row in group)
    {
        Console.WriteLine("{0}- {1}   {2}", ++rowNum, row.Field<string>("Address"), row.Field<string>("Address"));
    }
}