转换日期类型 C#

Question

I am Creating A Web app I am using a textbox and textbox calender extender to get the date enter by the user, I want Date in this ("dd-MM-yyyy") format,

but I am getting error

(Arithmetic overflow error converting expression to data type datetime.)

By Default the format of the date is ("yyyy-MM-dd") this

protected void txttodate_TextChanged(object sender, EventArgs e)
{
    string com = Convert.ToString(Session["radio"]);
    string com1 = Convert.ToString(Session["mysession"]);
    Session["drd3"] = com.ToString();
    Session["lblname"] = com1.ToString();

    SqlCommand cmdtr = new SqlCommand("select empname from trainerdetails where trid='"+com1.ToString()+"'",con);
    con.Open();
    SqlDataReader dr = cmdtr.ExecuteReader();
    while (dr.Read())
    {
        lblempname.Text = dr["empname"].ToString();
    }
    GridView1.Visible = true;
    connectionstr = WebConfigurationManager.ConnectionStrings["Constr"].ConnectionString;
    con = new SqlConnection(connectionstr);
    SqlCommand cmd = new SqlCommand("csuvdaterange");
    cmd.CommandType = CommandType.StoredProcedure;
    cmd.Connection = con;
    SqlParameter[] param =
    {
        new SqlParameter("@logintype",com.ToString()),
        new SqlParameter("@name",lblempname.Text),
        new SqlParameter("@datefrm",txtfrmdate.Text),
        new SqlParameter("@dateto",txttodate.Text)
    };
    cmd.Parameters.AddRange(param);
    SqlDataAdapter da = new SqlDataAdapter(cmd);
    DataSet ds = new DataSet();
    da.Fill(ds);
    GridView1.DataSource = ds;
    GridView1.DataBind();
}

This Is How My Backend Code looks

   <asp:TextBox ID="txtfrmdate" Visible="false" runat="server" placeholder="From" style="margin-left:10px; margin-top:8px;" Height="30px" Width="200px"></asp:TextBox>
   <asp:CalendarExtender ID="calenderfromextend" TargetControlID="txtfrmdate" runat="server" Format="dd-MM-yyyy"></asp:CalendarExtender>
   <asp:TextBox ID="txttodate" placeholder="To" Visible="false" runat="server" style="margin-left:10px; margin-top:8px;" AutoPostBack="true" OnTextChanged="txttodate_TextChanged" Height="30px" Width="200px"></asp:TextBox>
   <asp:CalendarExtender ID="calendertoextend" TargetControlID="txttodate" runat="server" Format="dd-MM-yyyy"></asp:CalendarExtender>

My Textboxes and calender extender

Answer 1

After Implementing Jon's suggestions on using Parameterised SQL , using using statements and if you are sure that the dates entered in TextBox are in format " yyyy-MM-dd ", you may use this code to change the format string:

SqlParameter[] param =
{
    new SqlParameter("@logintype",com.ToString()),
    new SqlParameter("@name",lblempname.Text),
    new SqlParameter("@datefrm",DateTime.ParseExact(txtfrmdate.Text, "dd-MM-yyyy", CultureInfo.InvariantCulture).ToString("yyyy-MM-dd")),
    new SqlParameter("@dateto",DateTime.ParseExact(txttodate.Text, "dd-MM-yyyy", CultureInfo.InvariantCulture).ToString("yyyy-MM-dd"))
};

Answer 2

First parse your textbox to a DateTime object by DateTime.ParseExact

var dateFrom = DateTime.ParseExact(txtfrmdate.Text, "dd-MM-yyyy", null);
var dateTo = DateTime.ParseExact(txttodate.Text, "dd-MM-yyyy", null);

After that, replace in your SqlParameter :

SqlParameter[] param =
{
    new SqlParameter("@logintype",com.ToString()),
    new SqlParameter("@name",lblempname.Text),
    new SqlParameter("@datefrm",SqlDbType.DateTime) { Value = dateFrom },
    new SqlParameter("@dateto", SqlDbType.DateTime) { Value = dateTo }
};

Answer 3

String.Format("{0:MM/dd/yyyy}", dt);