Accepted answer

As hinted at in Jeremy's answer, If you've a reference to System.Data.DataSetExtensions.dll, you'll get some handy extension methods for working with DataSets and DataTables using LINQ. Specifically, you can use the Field<int?>() method to convert an integer column that might contain DBNull into a column of nullable ints...

albumIds = dt.AsEnumerable().Select(row => row.Field<int?>("F1"))
                            .Where(val => val.HasValue)
                            .Select(val => val.Value)


I'll answer my own question.

Instead of using Linq I do a foreach loop and delete rows if value is null. and then do Linq distinct

            foreach(DataRow row in dt.Rows)
                if (String.IsNullOrEmpty(row["F1"].ToString()))


            albumIds = dt.AsEnumerable().Select(p => (int)p.Field<double>("F1")).Distinct().ToArray();


You just need to filter the null values out first. Then your LINQ expression should work great.


You need to check the fields for DBNull before you attempt the conversion using the Where method is probably easiest.

dt.AsEnumerable().Where(p => p.Field("F1") != DBNull.Value).Select(p => (int)p.Field("F1")).Distinct().ToArray();


Can you try this:

dt.AsEnumerable().Where(p => p.IsNull("F1") == false)
  .Select(p => p.Field<int>("F1")).Distinct().ToArray();

I can't really check this as I don't have this DB setup

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