How to assign value to HiddenField from SqlDataSource using C# in ASP.Net

I am attempting to populate a hidden field using a SqlDataSource that it triggered by the OnSelectedIndexChanged event of a dropdown list. Here is what I have tried.

protected void CompIdDdl_SelectedIndexChanged(object sender, EventArgs e)
        {
            SqlDataSource sdsCompRep = new SqlDataSource();
            sdsCompRep.ID = "sdsCompRep";
            this.Page.Controls.Add(sdsCompRep);
            sdsCompRep.ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;
            sdsCompRep.SelectCommand = "SELECT cr.compRepIdPk, cr.anuId, anu.FirstName, anu.LastName, anu.Email cr.compIdFk, c.compNm FROM compReps cr LEFT JOIN AspNetUsers anu ON cr.anuId = anu.Id LEFT JOIN comps c ON cr.CompIdFk = c.compIdPk";

            DataSourceSelectArguments args = new DataSourceSelectArguments();
            DataView view = (DataView)sdsCompRep.Select(args);
            DataTable dt = view.ToTable();

            if (dt.Rows.Count > 0)
            {                
                string compRepEmail = dt.Rows[0]["Email"].ToString();
                hdnRepEmail.Value = compRepEmail;
            }
        }

But I get the following error when I select an item in the dropdown list: System.Data.SqlClient.SqlException: 'Incorrect syntax near '.'.'