Question

C# - cannot get data from a database into a DataTable object

Asked by: josephdaviskcrm

What is wrong with this code?  I have verified that the connection string is correct and that the sql I pass actually returns data because I am able to get data back from the database into an sqlDataReader.  I thought this data_table method of mine worked, but I'm not getting back any data in the datatable.

Can anybody see a problem with the way I have this written?

public static void Data_Table(string strSQL, ref DataTable dt)
        {
            String strConn = @"Data Source=ARIZONA\SQLEXPRESS;Initial Catalog=Finances;Integrated Security=True";
            SqlConnection conn = null;
            SqlCommand cmd = null;
            SqlDataAdapter da = null;
 
            try
            {
                conn = new SqlConnection(strConn);
                cmd = new SqlCommand(strSQL, conn);
                da = new SqlDataAdapter();
                dt = new DataTable();
                cmd.Connection.Open();
                da.SelectCommand = cmd;
                da.Fill(dt);
            }
            catch (Exception ex)
            {
            }
            finally
            {
                da.Dispose();
                cmd.Dispose();
                conn.Dispose();
            }
        }

                                  
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Asked On
2009-04-18 at 11:17:10ID24334481
Topics

C# Programming Language

,

.NET

Participating Experts
4
Points
500
Comments
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Answers

 

by: tiagosalgadoPosted on 2009-04-18 at 11:27:20ID: 24176251

Change the "public static void Data_Table(string strSQL, ref DataTable dt)" to "public static DataTable Data_Table(string strSQL, ref DataTable dt)" and add a "return dt" after "da.Fill(dt);".

 

by: angelIIIPosted on 2009-04-18 at 11:29:54ID: 24176260

how do you use the function?
you have a datatable, and not datareader in there.

 

by: nkhelashviliPosted on 2009-04-18 at 11:29:58ID: 24176261

But where are you checking if the datatable is filled?

 

by: josephdaviskcrmPosted on 2009-04-18 at 11:31:10ID: 24176264

There is a DataTable object passed into the method in the parameter list.  The problem exists inside the method itself.  I've been stepping through the code and when I run da.Fill(dt) I'm not getting any data inside the dt object.

 

by: josephdaviskcrmPosted on 2009-04-18 at 11:32:37ID: 24176266

Here is an example of how I am calling the method...

dt = new DataTable();
            Data_Table("SELECT Date, Category, SUM(Amount) AS Amount FROM (SELECT  CAST(MONTH(DATE) AS VARCHAR) + '-' + RIGHT(CAST(YEAR(DATE) AS VARCHAR), 2) AS [Date], Amount, Category FROM Transactions WITH(NOLOCK) WHERE Account IN ('Spending') AND Category IS NOT NULL) a GROUP BY Date, Category ORDER BY Date, Category", ref dt);

 

by: nkhelashviliPosted on 2009-04-18 at 11:33:28ID: 24176269

Run sql profiler to check which select statement is executing

 

by: josephdaviskcrmPosted on 2009-04-18 at 11:34:08ID: 24176272

So the DataTable exists outside of the method and is passed in by reference.  So if the DataTable gets filled with Data I will have the data outside of the method also.

 

by: angelIIIPosted on 2009-04-18 at 11:35:44ID: 24176277

>There is a DataTable object passed into the method

if that is really the case, remove this line from the procedure:
dt = new DataTable();

 

by: josephdaviskcrmPosted on 2009-04-18 at 11:35:45ID: 24176278

what is sql profiler?

 

by: josephdaviskcrmPosted on 2009-04-18 at 11:37:28ID: 24176285

>There is a DataTable object passed into the method

>if that is really the case, remove this line from the procedure:
>dt = new DataTable();

I added that line after it wasn't working to see if it would fix anything, but of course it didn't.  I've taken it out now.

 

by: angelIIIPosted on 2009-04-18 at 12:22:25ID: 24176436

again, how do you CALL the procedure, please?

also, note that your function is eating up any exception, so you won't see if there is an error occurring!!

please check if your function code actually runs into an error.

 

by: nkhelashviliPosted on 2009-04-18 at 12:33:04ID: 24176465

>  also, note that your function is eating up any exception

yes,  add the line in the catch block


MessageBox.Show(ex.Message.ToString());

                                              
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by: sm394Posted on 2009-04-18 at 14:49:21ID: 24176903

Hi guys
below is a tested and working example
you can tweak according to your needs ie. passing query as param

usage is
DataTable dt = GetDataTable();

 public static DataTable GetDataTable()
        {
            SqlConnection con = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["dbConnection"].ConnectionString);
            SqlCommand cmd = new SqlCommand();
            cmd.CommandText = "select * from applications where id=@ID";
            cmd.Connection = con;
            cmd.CommandType = CommandType.Text;
            cmd.Parameters.Add(new SqlParameter("@ID", SqlDbType.Int, 8)).Value = 2;
            SqlDataAdapter sda = new SqlDataAdapter(cmd);
            DataTable dt = new DataTable();
            try
            {
                con.Open();
                sda.Fill(dt);
 
            }
            catch (SqlException err)
            {
               throw new ApplicationException("Data error." + err);
            }
            finally
            {
                con.Close();
                con.Dispose();
                
            }
            return dt;
 
        }

                                              
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