Error in Asp.net c#,Grid view,Data set,

Hai
When i select the values from drop down list the necessary details are showed
I have the following the code while it runs it displays the code:
SqlConnection objcon = new SqlConnection("Data Source=.;Initial Catalog=Iwens_Database;User ID=qwd;Password=123;Integrated Security=SSPI;");


SqlCommand objcom = new SqlCommand("SELECT * FROM dbo.Enquiry_table where DOEn >'" + FromTextBx.Text + "' AND DOEn<='" + ToTextBx.Text + "'", objcon);
SqlDataAdapter sda = new SqlDataAdapter();
// DataSet objds = new DataSet(); which is in command line
DataTable sdt = new DataTable();

sda.Fill(sdt );
BetweenGridView.DataSource = sdt;
BetweenGridView.DataBind();

The SelectCommand property has not been initialized before calling 'Fill'.