DataReader .HasRows but returns 'Invalid attempt to read when no data is present' error

  • Thread starter Thread starter Assimalyst
  • Start date Start date
A

Assimalyst

Hi,

I am using a stored procedure to extract data from an SQL server
database using a datareader.

The datareader .HasRows returns true, i have also checked this with
query analyser, but when i attempt to use a returned value to
SelectValue in a combobox I get the error 'Invalid attempt to read when
no data is present'. How can this be when .HasRows is true?

Here's the relevant code:

SqlCommand cmdLesion = new SqlCommand ("proc_SelectLesion", conn);
cmdLesion.CommandType = CommandType.StoredProcedure;

cmdLesion.Parameters.Add(new SqlParameter("@patientNo", strPatientNo));
cmdLesion.Parameters.Add(new SqlParameter("@lesLocation",
strLesionLocation));

conn.Open();

SqlDataReader dr;
dr = cmdLesion.ExecuteReader(CommandBehavior.SingleRow);

if(dr.HasRows)
{
lesionLocationCboBx.SelectedValue = dr["lesNo"].ToString();
}
else
{
lesionLocationCboBx.SelectedIndex = 0;
}

dr.Close();


And the stored procedure "proc_SelectLesion":

CREATE PROCEDURE proc_SelectLesion
(@patientNo int,
@lesLocation varchar(50)
)

AS

SELECT lesNo
FROM tbllesion
WHERE lesLocation = @lesLocation AND patientNo = @patientNo
GO

Any ideas?

Many thanks.
 
Assimalyst,

From the docs:

"The default position of the SqlDataReader is prior to the first record.
Therefore, you must call Read to begin accessing any data."

Kerry Moorman
 
I believe need to issue a Read() call to move to each row.

if(dr.HasRows)
{
dr.Read();
lesionLocationCboBx.SelectedValue = dr["lesNo"].ToString();
}
 
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