[Solved] UNION clause Error: Conversion failed when converting the varchar value to data type int

same query run in sql no error show. record display ok.

but query run c# error show

Conversion failed when converting the varchar value 'sushil' to data type int. 

i do not know where my error. pls check

public DataSet Selectedfrndshow(int ID)
{
    Sqlcon();
    string qry= "select top 6 * from ( "
    + " select a.to_id, a.from_id,b.first_name,b.last_name,b.id as 'bid',c.imagedata,c.id as 'cid' from tblfrequst a "
    + " join tbluserinfo b on a.to_id=b.id"
    + " join tbluserprofilepicture c on c.id=b.id"
    + " where a.from_id="+ID + " and a.request_status='AC'" 
    + " UNION"
    + " select a.to_id,a.from_id,b.id,b.first_name,b.last_name,c.imagedata,c.id from tblfrequst a "
    + " join tbluserinfo b on a.from_id=b.id " 
    + " join tbluserprofilepicture c on c.id=b.id"
    + " where a.to_id="+ID+ " and a.request_status='AC'"
    + ") tblfrequst";
    SqlDataAdapter adp = new SqlDataAdapter(qry, con);
    DataSet ds = new DataSet();
    adp.Fill(ds);
    if (ds.Tables[0].Rows.Count > 0)
    {
        return ds;
    }
    else
    {
        return null;
    }
}

private void SHOWHRND()
{
// try
// {
    DataSet odt;
    if (vid == Int32.Parse(Session["uid"].ToString()))
    {
        odt = MFL.Selectedfrndshow(Convert.ToInt32(Session["uid"].ToString()));
    }
    else
    {
        odt = MFL.Selectedfrndshow(vid);
    }
    if (odt != null)
    {
        if (odt.Tables[0].Rows.Count > 0)
        {
            DataList1.DataSource = odt;
            DataList1.DataBind();
        }

        lblerr.Visible = false;
        // lblfcnt.Text = odt.Tables[0].Rows.Count.ToString();
    }
// }
// catch (Exception ex)
// {
// lblerr.Visible = true;
// lblerr.Text = ex.Message.ToString();

// }
}