日期时间数据类型不匹配访问

Question

I am having a problem with this statement i am Trying to retrieve data from a table based on the date but its keep telling me that there is a data type mismatch

DateTime dt = DateTime.ParseExact(textBox1.Text, "dd/mm/yyyy", null);
            OleDbCommand cmd2 = new OleDbCommand("select name from Items where exp_dat='" + dt + "'", con);
            System.Data.DataTable dt4 = new System.Data.DataTable();
            OleDbDataAdapter Adapter4 = new OleDbDataAdapter(cmd2);
            Adapter4.Fill(dt4);
            dataGridView1.DataSource = dt4;

Answer 1

Use parameters to prevent sql injection and conversion/localization issues:

var dt4 = new System.Data.DataTable();
using(var da = new OleDbDataAdapter("select name from Items where exp_dat=@exp_dat", con))
{
    DateTime dt;
    if(DateTime.TryParseExact(textBox1.Text, "dd/mm/yyyy", DateTimeFormatInfo.InvariantInfo, DateTimeStyles.None, out dt))
    {
        da.SelectCommand.Parameters.Add("@exp_dat", OleDbType.Date).Value = dt;
        da.Fill( dt4 );
    }
}

Note that

• con.Open / con.Close is not needed with OlebDataAdapter.Fill(table)
• you should always use the using -statement on objects that are disposable(implement IDisposable ), that ensures that all unmanaged resources are disposed, even in case of an error
• you should use DateTimeFormatInfo.InvariantInfo or CultureInfo.InvariantCulture instead of null as parameter for ParseExact since null is replaced with the current culture. If that does not use / as date separator TryParseExact cannot parse this string(presuming that textBox1.Text is something like 28/09/2015 )