filtering GridView by DropDownList

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ASP.NET

Gridview

DropDownList

Hello
I have have a gridView with some data including a date field.
and I have a dropDownList contains the distinct dates of a table, and I assigned both the ID and the value to the date field.

protected void Page_Load(object sender, EventArgs e)

<pre lang="c#">{
    if (!IsPostBack)
    {
        DataAndConnManagment D = new DataAndConnManagment();
        D.FillDropDownList("Select Distinct MeetingDate from Meeting");
        DDLDates.DataSource = D.dr;
        DDLDates.DataTextField = "MeetingDate";
        DDLDates.DataValueField = "MeetingDate";
        DDLDates.DataBind();
        D.dr.Close();
    }
}

Now...

If I run the web-form without where condition, it runs without errors.
But if I added a where statment to the grid view
Meeting.MeetingDate = @Param1

...
some code
...

<asp:ControlParameter ControlID="DDLDates" Name="Param1" PropertyName="Text" />

then I receive the error "Exception Details: System.Data.SqlClient.SqlException: Conversion failed when converting datetime from character string."

I'll be appreciated if any body can help me.