How to check the date for three days before

protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)

{

if (e.CommandName.Equals("InsertData"))

{

DropDownList ddltrainname = GridView1.FooterRow.FindControl("ddltrainname") as DropDownList;

TextBox txtprfdate = GridView1.FooterRow.FindControl("txtprfdate") as TextBox;

TextBox txtprftime = GridView1.FooterRow.FindControl("txtprftime") as TextBox;

DropDownList ddlprffac = GridView1.FooterRow.FindControl("ddlprffac") as DropDownList;

DropDownCheckBoxes ddlEmployes = GridView1.FooterRow.FindControl("ddlEmployes") as DropDownCheckBoxes;

SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["connectionstring"].ConnectionString);

{

try

{

SqlCommand cmd = new SqlCommand("insert into RegisterfroTraining (NameofTraining,Prefdate,Preftime,Preffac,EmployeeID,Status) values (@NameofTraining,@Prefdate,@Preftime,@Preffac,@EmployeeID,@Status)");

cmd.CommandType = CommandType.Text;

cmd.Connection = con;

cmd.Parameters.AddWithValue("@NameofTraining", ddltrainname.Text);

cmd.Parameters.AddWithValue("@Prefdate", txtprfdate.Text);

cmd.Parameters.AddWithValue("@Preftime", txtprftime.Text);

cmd.Parameters.AddWithValue("@Preffac", ddlprffac.Text);

string EmployeeIDs = string.Empty;

foreach (ListItem item in ddlEmployes.Items)

{

if (item.Selected)

{

EmployeeIDs += item.Text + ",";

}

}

cmd.Parameters.AddWithValue("@EmployeeID", EmployeeIDs.Trim(','));

cmd.Parameters.AddWithValue("@Status", "Open");

if (con.State == ConnectionState.Closed)

{

con.Open();

}

cmd.ExecuteNonQuery();

BindGrid();

Page.RegisterStartupScript("Alert", "");

}

catch (Exception ex)

{

Exception ex2 = ex;

string errormessage = string.Empty;

while (ex2 != null)

{

errormessage += ex2.ToString();

ex2 = ex2.InnerException;

}

Page.RegisterStartupScript("Alert", "");

}

}

}

}