C# return value of a 'SELECT' query

Question

My connection string:

string connection = @"Provider=Microsoft.ACE.OLEDB.12.0;" +
    @"Data Source=\\reso-fs-2\allusers\Student_Home\20350657\Documents\clicker.accdb;" +
    @"Jet OLEDB:Database Password=" + "password" + ";";

OleDbConnection con = new OleDbConnection(connection);

So I have this query in C# OleDb:

string query = "SELECT stats_best FROM Users WHERE username="+GameForm.username;

I want to fetch the value from 'stats_best' and save it into a string. I have already set-up the connection and all that. I just need to return a value from the query. How can I do that?

Did you read anything about creating and executing a command? Please take some tutorials since this is the wrong way to learn... — Patrick Hofman, Mar 15 '16 at 10:16
[How to: Create and Execute an SQL Statement that Returns Rows](https://msdn.microsoft.com/en-us/library/fksx3b4f.aspx) — Patrick Hofman, Mar 15 '16 at 10:17
I tried executing commands but every time I get an exception that one of the variables is missing in runtime but everything is there. I looked into it and can't find a solution. — Pawel, Mar 15 '16 at 10:18
I don't want to return a row, I already know how to do that. I need to return a single value and save it into a string. — Pawel, Mar 15 '16 at 10:18
So what is the exception? What is the actual SQL statement executed? — Patrick Hofman, Mar 15 '16 at 10:19
I execute a OleDbCommand using OleDbDataReader and read the first value from the reader. I get the 'No value given for one or more required parameters.' exception on runtime. — Pawel, Mar 15 '16 at 10:21

score 0 · Answer 1 · answered Mar 15 '16 at 10:22

0

Please Read this article, but anyway, you can use this

public string Test(string userName, string connectionString, out string dbErrorMessage)
    {
        string result = null;
        dbErrorMessage = null;
        try
        {
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                connection.Open();
                SqlCommand cmd = connection.CreateCommand();
                cmd.Parameters.Add(new SqlParameter("@UserName", userName));
                cmd.CommandText = "SELECT stats_best FROM Users WHERE username= @UserName";
                result = cmd.ExecuteScalar().ToString();
            }
        }
        catch (Exception ex)
        {
            dbErrorMessage = ex.Message;
        }
        return result;
    }

and the usage of method:

string dbErrorMessage = null;
Test(GameForm.username, connectionString, out dbErrorMessage);

answered Mar 15 '16 at 10:22

SᴇM

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This seems to execute but it doesn't return the value from the database. – Pawel Mar 15 '16 at 10:27
did you check your `ConnectionString`? – SᴇM Mar 15 '16 at 10:28
I can't check your connection string from here, please check if it works. And what is result of execution? – SᴇM Mar 15 '16 at 10:31
The program executes but doesn't return a value. Maybe it's because i'm using OleDbConnection rather than SqlConnection. Could this method be adapted to OleDbConnection? – Pawel Mar 15 '16 at 10:33
`"Data Source=\\reso-fs-2\allusers\Student_Home\20350657\Documents\clicker.accdb;Initial Catalog=;User=;Password=;"`, something like this – SᴇM Mar 15 '16 at 10:40
Nothing seems to be returning the string. Thank you for your help though. – Pawel Mar 15 '16 at 10:50

C# return value of a 'SELECT' query

1 Answers1