Applying Linq on DataTables in c#

Question

I have 2 data tables in C# Say dt1 and dt2. I need to fetch records from dt1 which are not present in dt2 on the basis of a Reference Id and need to select multiple columns via LINQ.

@MrinalKamboj you shouldn't have approved that edit. Don't use inline code to highlight random terms. — CodeCaster
– CodeCaster, Commented Sep 19, 2016 at 10:43
var results = (from DataRow dr1 in dt1.AsEnumerable() where !(from DataRow dr2 in dt2.AsEnumerable() select cao["dr2"]).Contains(cs["OID"]) select new { col1 = cs["RefId"], col2 = cs["Id"]}); I have used this code but need something faster than this. — Harshit
– Harshit, Commented Sep 19, 2016 at 11:58

Gerald Gonzales · Accepted Answer · 2016-09-19 10:51:40Z

1

You can try this:

var result = dt1.AsEnumerable()
             .Where(p => !dt2.AsEnumerable().Any(p2 => p2["id"] == p["id"]))
             .CopyToDataTable();

You have plenty of options. You can also try the LINQ EXCEPT.

edited Sep 19, 2016 at 10:51

answered Sep 19, 2016 at 10:29

Gerald Gonzales

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4 Comments

Mrinal Kamboj Over a year ago

Linq API are extension methods to IEnumerable<T>, it cannot be applied to the DataTable directly, use AsEnumerable for DataTable to call Linq APIs

Gerald Gonzales Over a year ago

@MrinalKamboj - Thank you, I forgot that part. I updated my answer.

Mrinal Kamboj Over a year ago

Even now its incorrect, since DataTable's AsEnumerable yields IEnumerable<DataRow>, not the type T as expected. You need DataRow[<ColumnName>] to fetch a value.

Mrinal Kamboj Over a year ago

This shall, though the complexity would be O(N^2), +1 for the effort and modification to produce correct result

Community · Accepted Answer · 2017-05-23 12:32:43Z

1

You need to modify the DataRowComparer as per requirement, as I am currently only comparing Primary Key (replace with actual column name), check for reference, how to do it using multiple columns C# Errors when doing a simple datarow comparer

 var result = dt1.AsEnumerable().Except(dt2.AsEnumerable(), new  DataRowComparer()).CopyToDataTable();

public class DataRowComparer : IEqualityComparer<DataRow>
{
    /// <summary>
    /// Whether the two strings are equal
    /// </summary>
    public bool Equals(DataRow x, DataRow y)
    {
        return x["PrimaryKey"] == y["PrimaryKey"];
    }

    /// <summary>
    /// Return the hash code for this string.
    /// </summary>
    public int GetHashCode(DataRow dataRow)
    {
        return dataRow["PrimaryKey"].GetHashCode(); 

    }
}

edited May 23, 2017 at 12:32

CommunityBot

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answered Sep 19, 2016 at 11:04

Mrinal Kamboj

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