Question

I get a Conversion failed error when converting DateTime from character string, any help?

sqlcon.Open();
sqlcmd = new SqlCommand("select [Uzsak_Nr],[Preke],[Uzsak_Kiekis],[Gaut_Kiekis],[MyDate],[Gaut_Data] from emp where MyDate between '" + TextBoxData1  + "'  and  '" + TextBoxData2 + "' ", sqlcon);
da = new SqlDataAdapter(sqlcmd);
da.Fill(dt);
GridViewRodyti.DataSource = dt;
GridViewRodyti.DataBind();
sqlcon.Close();

Answer 1

This has got SQL Injection written all over it…

Use parameterized queries e.g.

var sqlCmd = new SqlCommand("select [Uzsak_Nr],[Preke],[Uzsak_Kiekis],[Gaut_Kiekis],[MyDate],[Gaut_Data] from emp where MyDate between '@startDate' and '@endDate'", sqlcon);
sqlCmd.Parameters.Add(new SqlParameter("@startDate", DateTime.Parse(TextBoxData1)));
sqlCmd.Parameters.Add(new SqlParameter("@endDate", DateTime.Parse(TextBoxData2)));

Your issue is probably due to an invalid date format, if you use SqlParameter and convert the string to a DateTime it should take care of the conversion for you.