Question

Sorry, Im just learning LINQ and am relatively new at it.

Is it possible to convert the following into LINQ?

foreach (DataRow gradeCount in GraceTable.Rows)
{
    if (Convert.ToDecimal(obtMarksRow["Percentage"]) >= 
        (Convert.ToDecimal(gradeCount["EXG_MARKS_ABOVE"])) &&
        (Convert.ToDecimal(obtMarksRow["Percentage"]) <= 
        Convert.ToDecimal(gradeCount["EXG_MARKS_BELOW"])))
    {
        string Grade = Convert.ToString(gradeCount["EXG_GRADE_NAME"]);
    }
}

Edit : sorry i missed for each loop in ma query and obtMarksRow comes from one more loop which is outside this

I wrote the query like this

     var gradeValue = from DataRow gradeRow in GraceTable.Rows
                                 let marksAbove = gradeRow.Field<decimal>("EXG_MARKS_ABOVE") 
                                 let marksBelow = gradeRow.Field<decimal>("EXG_MARKS_BELOW")
                                 where obtMarksRow.Field<decimal>("Percentage") >= marksAbove && obtMarksRow.Field<decimal>("Percentage") <= marksBelow
                                 select gradeRow.Field<string>("EXG_GRADE_NAME");

but i am getting the value (gradeValue.ToString() ) as “System.Linq.Enumerable+WhereSelectEnumerableIterator`2[System.Data.DataRow,System.String]”

Whats wrong ?

Answer 1

No, it isn’t possible. As the commenters point out, LINQ is for querying collections of things. You don’t appear to have a collection here: just an if statement and an assignment.

Furthermore, be careful about trying to convert things to LINQ unnecessarily. As you start to understand LINQ better, you’ll find yourself naturally using it for a variety of purposes. But starting off with the assumption that code will be better with LINQ is probably a fallacy.

Edit

As mentioned earlier, LINQ is about querying a collection for a set of results. If you only want one result, you can use Single, First, SingleOrDefault, or FirstOrDefault to get it out of the resulting collection.

 var gradeValues = from DataRow gradeRow in GraceTable.Rows
                             let marksAbove = gradeRow.Field<decimal>("EXG_MARKS_ABOVE") 
                             let marksBelow = gradeRow.Field<decimal>("EXG_MARKS_BELOW")
                             where obtMarksRow.Field<decimal>("Percentage") >= marksAbove && obtMarksRow.Field<decimal>("Percentage") <= marksBelow
                             select gradeRow.Field<string>("EXG_GRADE_NAME");

var firstGradeValue = gradeValues.First(); // will throw exception if there were no matches.
Console.WriteLine(firstGradeValue);