从索引 34 处开始，初始化字符串的格式不符合规范

public partial class Default2 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
          string Constr = "Provider =Microsoft.Jet.OLEDB.4.0;Data Source" + Server.MapPath("user.mdb");
         OleDbConnection conn = new OleDbConnection(Constr);
        try
        {
            //打开数据库
            conn.Open();
            OleDbDataAdapter oa = new OleDbDataAdapter("select * from what", conn );
            DataSet ds = new DataSet();
            oa.Fill(ds, "custom");
            GridView1.DataSource = ds;
            GridView1.DataBind();
        }
        catch { }
        finally
        {
            //关闭数据库
            conn.Close();
        }
    }
    protected void GridView1_PageIndexChanging(object sender, GridViewPageEventArgs e)
    {
        GridView1.PageIndex = e.NewPageIndex;
        GridView1.DataBind();
    }
}
问题出现在红色这里，请各位帮帮忙看下！

[ 本帖最后由 易小川 于 2011-3-20 16:59 编辑 ]