Bind Data Into DropDownLIst

SqlConnection con = new SqlConnection("ConnectionString");
SqlDataAdapter da = new SqlDataAdapter("Select * from TableName",con);
DataTable dt = new DataTable();
da.Fill(dt);

ddlcategory.DataSource = dt;
ddlcategory.DataTextField = "Name";
ddlcategory.DataValueField = "Id";
ddlcategory.DataBind();
ddlcategory.Items.Insert(0, "---select---");