To prevent from sql injection, Always use Parameterised Query.
Try like this,
SqlCommand cmd = new SqlCommand("select * from Docket where yourDate between @FromDate and @ToDate", con);
DateTime FromDate;
DateTime Todate;
System.Globalization.CultureInfo culmoney = new System.Globalization.CultureInfo("hi-IN",true);
FromDate = DateTime.Parse(txtFromDate.Text.Trim(), cul, System.Globalization.DateTimeStyles.NoCurrentDateDefault);
Todate = DateTime.Parse(txtTodate.Text.Trim(), cul, System.Globalization.DateTimeStyles.NoCurrentDateDefault);
cmd.Parameters.AddWithValue("@FromDate", FromDate.ToShortDateString());
cmd.Parameters.AddWithValue("@ToDate", Todate.ToShortDateString());