lets go one by one

dt is your datatable variable

where **dt.AsEnumerable** will segregate the datatable to datarows

then SUM is a Aggregate Function

which will sum all the values in the specified column in this expression

**Function(x) If(IsNumeric(x(“ColumnName”).ToString.Trim),CDbl(x(“ColumnName”).ToString.Trim),0)**

where this function does a validation like only if the value in each cell of that column along each row is NUMERIC then it will be considered for SUMMATION else taken as 0

Cheers @Mayur_Pawar