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c#linqlinq-to-sql
Tipx
Tipx

Reputation: 7515

Convert Linq Query Result to Dictionary

I want to add some rows to a database using Linq to SQL, but I want to make a "custom check" before adding the rows to know if I must add, replace or ignore the incomming rows. I'd like to keep the trafic between the client and the DB server as low as possible and minimize the number of queries.

To do this, I want to fetch as little information as required for the validation, and only once at the beginning of the process.

I was thinking of doing something like this, but obviously, it doesn't work. Anyone have an idea?

Dictionary<int, DateTime> existingItems = 
    (from ObjType ot in TableObj
        select (new KeyValuePair<int, DateTime>(ot.Key, ot.TimeStamp))
    )

What I'd like to have at the end would be a Dictionary, without having to download the whole ObjectType objects from TableObject.

I also considered the following code, but I was trying to find a proper way:

List<int> keys = (from ObjType ot in TableObj orderby ot.Key select ot.Key).ToList<int>();
List<DateTime> values = (from ObjType ot in TableObj orderby ot.Key select ot.Value).ToList<int>();
Dictionary<int, DateTime> existingItems = new Dictionary<int, DateTime>(keys.Count);
for (int i = 0; i < keys.Count; i++)
{
    existingItems.Add(keys[i], values[i]);
}

Upvotes: 435

Views: 436224

Answers (4)

tvanfosson
tvanfosson

Reputation: 532635

Try using the ToDictionary method like so:

var dict = TableObj.Select( t => new { t.Key, t.TimeStamp } )
                   .ToDictionary( t => t.Key, t => t.TimeStamp );

Upvotes: 776

Salman Mushtaq
Salman Mushtaq

Reputation: 53

Use namespace

using System.Collections.Specialized;

Make instance of DataContext Class

LinqToSqlDataContext dc = new LinqToSqlDataContext();

Use

OrderedDictionary dict = dc.TableName.ToDictionary(d => d.key, d => d.value);

In order to retrieve the values use namespace

   using System.Collections;

ICollection keyCollections = dict.Keys;
ICOllection valueCollections = dict.Values;

String[] myKeys = new String[dict.Count];
String[] myValues = new String[dict.Count];

keyCollections.CopyTo(myKeys,0);
valueCollections.CopyTo(myValues,0);

for(int i=0; i<dict.Count; i++)
{
Console.WriteLine("Key: " + myKeys[i] + "Value: " + myValues[i]);
}
Console.ReadKey();

Upvotes: 1

BFree
BFree

Reputation: 103760

Looking at your example, I think this is what you want:

var dict = TableObj.ToDictionary(t => t.Key, t=> t.TimeStamp);

Upvotes: 137

JaredPar
JaredPar

Reputation: 755317

Try the following

Dictionary<int, DateTime> existingItems = 
    (from ObjType ot in TableObj).ToDictionary(x => x.Key);

Or the fully fledged type inferenced version 

var existingItems = TableObj.ToDictionary(x => x.Key);

Upvotes: 11

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