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]);
}
This question is related to
c#
linq
linq-to-sql
todictionary
Try using the ToDictionary
method like so:
var dict = TableObj.ToDictionary( t => t.Key, t => t.TimeStamp );
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();
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);
Looking at your example, I think this is what you want:
var dict = TableObj.ToDictionary(t => t.Key, t=> t.TimeStamp);
Source: Stackoverflow.com