How do I get my gridview to display

It is happening because when you click the button the page is post back to the server and there you are with no data, as HTTP protocol is used.
So modify your code this way,

protected void btnDisplay_Click(object sender, EventArgs e)
        {
if(!IsPostBack)
            string connString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=H:\levels.mdb";
            DataSet ds;
            using (OleDbConnection myConnString = new OleDbConnection())
            {
                myConnString.ConnectionString = connString;
                using (OleDbCommand selectCommand = new OleDbCommand())
                {
                    selectCommand.CommandText = "select * from tblTest";
                    selectCommand.Connection = myConnString;
                    myConnString.Open();
                    using(OleDbDataAdapter da = new OleDbDataAdapter())
                    {
                        da.SelectCommand = selectCommand;
                        ds = new DataSet();
                        da.Fill(ds, "test");
 
                        GridView1.DataSource = ds;
                        GridView1.DataBind();
                    }                    
                }                
            }          
}     
        }//end click event

Hi,

You have coded like this,

selectCommand.CommandText = "select * from tblTest";

da.Fill(ds, "test");

Here you need give the actual name of the selected table. Like this

da.Fill(ds, "tblTest");

Please try this and update me,

SqlConnection con = new SqlConnection(@"Data Source=.;Initial Catalog=emp;Integrated Security=True");
    SqlDataAdapter sda;
    protected void Button1_Click(object sender, EventArgs e)
    {
        sda=new SqlDataAdapter("select * from tbl_emp",con);
        DataSet ds=new DataSet();
        sda.Fill(ds);
        GridView1.DataSource=ds.Tables[0];
        GridView1.DataBind();
     
    }

Try this

I hope it i'll help you

protected void btnDisplay_Click(object sender, EventArgs e)
{
string connString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=H:\levels.mdb";
DataTable dt;
using (OleDbConnection myConnString = new OleDbConnection())
{
myConnString.ConnectionString = connString;
using (OleDbCommand selectCommand = new OleDbCommand())
{
selectCommand.CommandText = "select * from tblTest";
selectCommand.Connection = myConnString;
myConnString.Open();
using(OleDbDataAdapter da = new OleDbDataAdapter())
{
da.SelectCommand = selectCommand;
ds = new DataSet();
da.Fill(dt);

GridView1.DataSource = dt;
GridView1.DataBind();
}
}
}
}//end click event

Try this

protected void btnDisplay_Click(object sender, EventArgs e)
{
SqlConnection sqlConnection = new SqlConnection(@"ConnectionString");
SqlDataAdapter dataAdapter;
DataSet dataSet=new DataSet();

dataAdapter=new SqlDataAdapter("select * from tbl_emp",sqlConnection);
dataAdapter.Fill(dataSet,'Employee');
GridView1.DataSource=dataSet.Tables['Employee'];
GridView1.DataBind();
}//end click event

Check your (ds.Tables[0].Rows.Count >0) or not and then
replace

GridView1.DataSource = ds.Tables[0];
 GridView1.DataBind();

in place of

 GridView1.DataSource = ds;
 GridView1.DataBind();

http://msdn.microsoft.com/en-us/library/bh8kx08z(v=vs.110).aspx[^]

I think your is not return any result ...Chech your dataset in step by step compilation(f11)