How to calculate summary total from currencies value in Business Process

Hello,

First of all you read only 1 record in the "Read Insurance" read data element (it can be seen from the "First item of resulting collection" macro value). The sum of this will always be the value you read. I think something else was intended here.

Next, you can use Enumerable.Sum method, but you need to get an enumerable. Or introduce a method that can be called inside a script task like (and add Terrasoft.Core.DB to the process usings):

protected decimal GetInsurancePremiTotal(Guid insuranceTypeId) { //or any other argument suitable
    var query = (Select)new Select(UserConnection)
        .Column(Func.Sum("UsrPremi")).As("TotalPremi")
        .From("UsrInsurance").As("usrInsurance").WithHints(new NoLockHint())
        .Where("usrInsurance", "UsrTypeId").IsEqual(Column.Parameter(insuranceTypeId));
    decimal totalPremi = 0;
    using (DBExecutor executor = UserConnection.EnsureDBConnection()) {
        totalPremi = query.ExecuteScalar<decimal>(executor);
    }
    return totalPremi;
}

And set the result to process parameter and then use this parameter value to proceed in the business process.