Use this LINQ in Assign activity.
dt.AsEnumerable() _
.Where(Function(row) Not String.IsNullOrEmpty(row.Field(Of String)("Amount"))) _
.Sum(Function(row) Convert.ToDecimal(row.Field(Of String)("Amount")))
Use this LINQ in Assign activity.
dt.AsEnumerable() _
.Where(Function(row) Not String.IsNullOrEmpty(row.Field(Of String)("Amount"))) _
.Sum(Function(row) Convert.ToDecimal(row.Field(Of String)("Amount")))