Cannot reterive date from textbox and send in to object?

protected void Hardware_add_Click(object sender, EventArgs e)
{
SqlConnection con = new SqlConnection(strConn);
con.Open();
SqlCommand ObjHardwarecmd = new SqlCommand("insert into Asset_Hardwaredetails(@hardware_id,@hardware_name,@vendor_name,@manufacturer,@hardware_description,@hardware_model,@purchase_date,@valid_up_to,@price)", con);
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,SqlParameter Parampurchase_date=newSqlParameter("@purchase_date",SqlDbType.Date);
SqlParameter Paramvalid_up_to=new SqlParameter("@valid_up_to",SqlDbType.Date);

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Parampurchase_date.Value = txtFdueon.Text;
Paramvalid_up_to.Value = txtvalid_up_to.Text;


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SqlParameter[] ObjHardware = { Paramhard_id,Paramhardware_name, Paramvendor_name, Parammanufacturer, Paramhardware_desctiption, Paramhardware_mode, Parampurchase_date, Paramvalid_up_to, Paramprice };
ObjHardwarecmd.Parameters.AddRange(ObjHardware);
ObjHardwarecmd.ExecuteNonQuery();
Response.Redirect("Hardware_view.aspx");

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Parampurchase_date.Value = txtFdueon.Text;
Paramvalid_up_to.Value = txtvalid_up_to.Text;

cant put .Text after txtFdueon and txtvalid_up_to ?????