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Generic LINQ Usage To Return Single Value From DataRow

, 15 Jul 2010 CPOL
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This tip will allow you to return the value from column X, where column Y matches your filter
I've used LINQ to objects for ever, but have stayed away from LINQ to sql for a while, because we don't exclusive use SQL Server.
 
I recently began toying with the System.Data.DataSetExtensions, and realized LINQ was a much faster (easier to code anyways) way to get the value from a DataColumn out of a DataTable.
 
Let's say I have a table of persons names, and I want to get the last name where the person_id = 100. I used to do something like this:
 
var persons = new DataTable();
 
string lastName = string.Empty;
 
DataRow[] foundRows = persons.Select("Person_Id = 100");
if (foundRows.Length == 1)
{
    lastName = foundRows[0]["Last_Name"].ToString();
}
 
now with LINQ, I have created the following method:
        
public static T GetFirstResultValue<t,ty>(DataTable table,string colToSearch, string colToReturn, TY searchValue) where TY: IComparable
{
    T ret = default(T);
 
    IEnumerable<datarow> rows = from row in table.AsEnumerable()
                                        where row.Field<ty>(colToSearch).CompareTo(searchValue) == 0
                                        select row;
 
    if (rows.Count() == 1)
    {
        ret = (T) rows.First()[colToReturn];
    }
 
    return ret;
}</ty></datarow>
 
This particular method will only work if the results of the search return 1 row, but it could easily be tweaked to return the DataRow collection, or an IEnumerable list of column values for the found rows.
 
Hope this helps someone!

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This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Paul Brower
Choice Genetics US
United States United States
Seasoned IT Professional. Currently the IT Director for Choice Genetics, and also the world-wide manager for IT Projects related to R&D for Groupe Grimaud (our parent company).
 
I've spent about half my career as a contractor. I've lived all over the place, but currently reside near St. Louis, Missouri. Moved out here from Roseville, California in Feb-2005. No regrets yet.
 
Over the recent years I've written software for:
- Disposing of radioactive and toxic waste.
- Disposing of surplus inventory during the Decommission of McClellan Air Force Base.
- Facilitating genetic improvement for Swine Breeding.
- Managing children placed in State custody.
- Dealing with commercial trucking delivery schedules.
- Tracking high resolution images from archeological digs.
- Project Management for the roofing industry.
- Processing engines for credit card transactions.
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