How can I sum the items result of query using foreach

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C#

MySQL

C#7.0

I'm trying to calculate the sum of MySQL data rows column table (ColumnSum) where data in columnkey = 999 using c# with entities query !
error shows at line

int TimeFab = int.Parse(item.ColumnSum);

:
Input string was not in a correct format.

What I have tried:

DatabaseEntities  ET = new DatabaseEntities  () ;
int TimeFabricate =0;
var query = from Time in ET where Time.Columnkey == "999"  select new { Time.ColumnSum };

var result = query.ToList();

foreach (var item in result)
{
    int TimeFab = int.Parse(item.ColumnSum);
   TimeFabricate +=  TimeFab;

              }

MessageBox.Show(TimeFabricate.ToString());