根据下拉列表选择的日期值填充GridView

我正在编写asp.net c#代码，以便使用sql查询和下拉列表填充Gridview。场景如下:

1. 如果下拉列表所选值为空，则选择所有来自数据库(select * from table)并填充GridView。这在visual studio 2008和服务器机器中都可以完美地工作。
2. 如果下拉列表选择的值是一个日期(这个日期是从数据库中选择的，所以它应该匹配数据库中的一个列值)，然后从表中选择*，其中date =下拉列表。选择的值。如果我使用Visual Studio 2008运行它，这个是有效的，但是给某个值一个空网格或一个错误，说

将char数据类型转换为日期时间数据类型导致日期时间值超出范围

//Page Load
protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        Condtion = "";
        this.BindGrid(Condtion);
    }
}

//Fill Grid View
private void BindGrid( String Condtion )
{
    string strConnString = ConfigurationManager.ConnectionStrings["ICIRDATAConnectionString1"].ConnectionString;
    using (SqlConnection con = new SqlConnection(strConnString))
    {
        String Qsql = "Select * from WeeklyReportView " + Condtion + "";
        using (SqlCommand cmd = new SqlCommand(Qsql))
        {
            using (SqlDataAdapter sda = new SqlDataAdapter())
            {
                cmd.Connection = con;
                sda.SelectCommand = cmd;
                using (DataTable dt = new DataTable())
                {
                    sda.Fill(dt);
                    GridView1.DataSource = dt;
                    GridView1.DataBind();
                }
            }
        }
    }
}
//Drop down List Selected Index Changed
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
    DateTime dt;
    if(DropDownList1.SelectedValue!="1")
    {
        dt = DateTime.ParseExact(DropDownList1.SelectedValue, "dd/MM/yyyy hh:mm:ss", new CultureInfo("en-GB"));
        Condtion1 = "wr_week='" + dt + "'";
    }
    Condtion2 = "eng_name='" + DropDownList2.SelectedValue + "'";
    if (DropDownList1.SelectedValue != "1" && DropDownList2.SelectedValue != "1")
    {
        Condtion = "Where " + Condtion1 + " and " + Condtion2;
    }
    else if (DropDownList2.SelectedValue != "1" && DropDownList1.SelectedValue == "1")
    {
        Condtion = "Where " + Condtion2;
    }
    else if (DropDownList2.SelectedValue == "1" && DropDownList1.SelectedValue != "1")
    {
        Condtion = "Where " + Condtion1;
    }
    else
    {
        Condtion = "";
    }
    this.BindGrid(Condtion);
}

有谁能帮忙吗?

dt = DateTime.ParseExact(DropDownList1.SelectedValue, "dd/MM/yyyy hh:mm:ss", new CultureInfo("en-GB"));
    Condtion1 = "wr_week='" + dt + "'";

dt = DateTime.ParseExact(DropDownList1.SelectedValue, "dd/MM/yyyy hh:mm:ss", new CultureInfo("en-GB"));
var datestring = dt.ToString("yyyy-MM-dd HH:mm:ss");
    Condtion1 = "wr_week=convert(datetime, '"+ datestring  +"', 121)";

select * from table where date='"+DropDownList1.SelectedItem.ToString()+"';

     dt = DateTime.Parse(DropDownList1.SelectedValue,System.Globalization.CultureInfo.InvariantCulture); 
     string ouputDate = dt.ToUniversalTime().ToString("dd/MM/yyyy hh:mm:ss",System.Globalization.CultureInfo.InvariantCulture);
     Condtion1 = "wr_week='" + ouputDate + "'";