How to store data to variable from SQL query in ASP net?

Question

So here is my code. What I'm trying to do store double rate_num value to number variable. But it is still getting an error.

String conn = ConfigurationManager.ConnectionStrings["DBConnectionString"].ConnectionString;
    string query = "select " + rate_from + " from Exchange_rate where ERates_Status = 'Active'";
    SqlConnection sqlcon = new SqlConnection(conn);
    sqlcon.Open();
    SqlCommand cmd = new SqlCommand(query, sqlcon);
    SqlDataReader reader = cmd.ExecuteReader();

    double number = "";

    while (reader.Read())
    {
        double rate_num = reader.GetDouble(0);

        number = rate_num
    }

    number;

    sqlcon.Close();

there is red underline in the number variable, below the bracket — Juli Andika
– Juli Andika, Commented Jul 10, 2019 at 7:35
What is the error message? When you hover your mouse over the red line, what does it say? — Mahmood Dehghan Tazereh
– Mahmood Dehghan Tazereh, Commented Jul 10, 2019 at 7:38
Only assignment, call, increment, decrement, await, and new object expressions can be used as a statement — Juli Andika
– Juli Andika, Commented Jul 10, 2019 at 7:41
double number = ""; causes an error. double number = 0; will do the (guessed) expected. And number; will surely cause a compiler error. not sure which result you expect here. — Christoph Biegner
– Christoph Biegner, Commented Jul 10, 2019 at 12:49

Christoph Biegner · Accepted Answer · 2019-07-10 07:41:23Z

1

I have two findings here:

number += rate_num;

I guess you want a sum of the rates. Since number is defined as a string you will get a string as result where all rates are concatenated. Define number as double:

double number = 0;

Second is the line after the while-loop:

number;

What do you want to archive here? This line will not compile neither if number is a string nor double. If this code is part of a method you pssibly want to return the calculated sum of rates. So you could

return number;

But first close your DB connection

answered Jul 10, 2019 at 7:41

Christoph Biegner

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