This is my oop code for selecting patients:

namespace HospitalAction
{
public class Patients
{
private string connectionString;
public Patients()
{
connectionString = @"Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\medicalDB.mdf;Integrated Security=True;User Instance=True";
}
public DataSet GetPatient(int patientID)
{
string query = "SELECT * FROM patient WHERE registration_id =@Registration_ID";
SqlCommand cmd = new SqlCommand(query);
cmd.Parameters.AddWithValue("@Registration_ID", patientID);
return FillDataSet(cmd, "Patient";
}
public DataSet GetPatient()
{
string query = "SELECT * FROM patient";
SqlCommand cmd = new SqlCommand(query);
return FillDataSet(cmd, "Patients";
}

private DataSet FillDataSet(SqlCommand cmd, string tableName)
{
SqlConnection con = new SqlConnection(connectionString);
cmd.Connection = con;
SqlDataAdapter adapter = new SqlDataAdapter(cmd);

DataSet ds = new DataSet();
try
{
con.Open();
adapter.Fill(ds, tableName);

}
finally
{
con.Close();
}
return ds;
}
}

this is the code in my form to load the data:
HospitalAction.Patients DB = new HospitalAction.Patients();

dataGridView1.DataSource = DB.GetPatient();

but its not showing anythhing on the datagrid and reports no error. thanks.

Add this line of code:
dataGridView1.databind();

its showing this error:
Error 1 'System.Windows.Forms.DataGridView' does not contain a definition for 'databind' and no extension method 'databind' accepting a first argument of type 'System.Windows.Forms.DataGridView' could be found (are you missing a using directive or an assembly reference?) C:\Users\DENRELE\Documents\Visual Studio 2010\Projects\HospitalManagementSystem\HospitalManagementSystem\Employeedata.cs 30 32 HospitalManagementSystem

Sorry, thought it was web-form;
delete previous and add this line:

dataGridView1.AutoResizeColumns(DataGridViewAutoSizeColumnsMode.AllCellsExceptHeader);

Also please check the following:
1
Remove the try block that you used before your open method OR add catch block that will display error message in case there is problem with your form connecting to your database.

2
With the above, if there is no error msg and no record is displayed, confirm that your dataset has records in it.

my friend wrote the oop class but he is not around, i jst notice that select statement comes before the database was opened, dunno how to fix that, but im working on it, any help will be greatly accepted.

Replace this block

try
{
con.Open();
adapter.Fill(ds, tableName);

}
finally
{
con.Close();
}


with

con.Open();
adapter.Fill(ds, tableName);
con.Close();

... please let me know if there is any error msg.

no error, but its not displaying anything in the grid, there are data in the table.

Use the step through tool in Visual Studio to step through your code when it is executing, check if the dataset "ds" has record in it before you bind it to your datagridview.

a) When using an Adapter, the Adapter really takes care of the connection opening and closing, so that does not seem to be where the problem you are having is from.

b) If you take a close look at what your GetPatient() method is doing, you probably need to make sure your dataset even contains the information you expect it to. Put a break point there and try to take a peek using the "Add Watch" debug functionality to make sure it is returning you data from the database.

c) Also where you access the data in your dataset, try specifying the tablename

HospitalAction.Patients DB = new HospitalAction.Patients();

dataGridView1.DataSource = DB.GetPatient().Tables[tablename];

It did not work really, this one works though...
public DataTable GetPatientMJ()
{

SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM patient", connectionString);
DataTable dt = new DataTable();

da.Fill(dt);
return dt;
}
I called it this way:
dataGridView1.DataSource = DB.GetPatientMJ();

Thanks though.