按LINQ中的第一个字母按单词列表分组

Question

I have to group by first letter of the word in LINQ. Since i'm new to LINQ i'm not aware of debugging into it.

//Code

var words4 = testDS.Tables["Words4"].AsEnumerable();

var wordGroups =
    from w in words4
    group w by w.Field<string>("word")[0] into g
    select new {FirstLetter = g.Key, Words = g };

foreach (var g in wordGroups)
{
    Console.WriteLine("Words that start with the letter '{0}':", g.FirstLetter);  
    Console.WriteLine(g.Field<string>("word"));

}

Its throwing "Invalid Arguments" execption in the last Console.WriteLine.

Answer 1

Try Adding a loop inside so you can get the results more accurately.

Replace:

Console.WriteLine(g.Field<string>("word"));

With:

foreach (var w in g.Words)
{
    Console.WriteLine(w.Field<string>("word"));
}

Answer 2

Since in your select , you created an anonymous object with field specified as Words and later you are accessing it through word , Also the Field extension method is not required.

You need to replace:

Console.WriteLine(g.Field<string>("word"));

with

Console.WriteLine(g.Words);

Answer 3

First, rather than your group consisting of DataRows, since you only want to show the words, I would select the words you want out of the datarow. Second, remember that the words are in a list. If you want to print them out, you'll need to loop or do something like string.Join (as I do below). For example:

var wordGroups =
    from w in words4.Select(w => w.Field<string>("word"))
    group w by w[0] into g
    select new { FirstLetter = g.Key, Words = g };

foreach (var g in wordGroups) {
    Console.WriteLine("Words that start with the letter '{0}':", g.FirstLetter);
    Console.WriteLine(string.Join(", ", g.Words));
}

Answer 4

This should fetch what you want from within wordGroups , using Linq syntax:

Replace:

Console.WriteLine(g.Field<string>("word"));

with:

g.Words.ForEach(w => Console.WriteLine(W.Field<string>("word"));

Answer 5

另一个选择是这样的吗？

Dictionary<string, List<Product>> groupedDictionary = _db.Products.GroupBy(g => g.Name.Substring(0,1)).ToDictionary(g => g.Key, g => g.ToList());