"Failed to convert parameter value from a SqlParameter to a DateTime." & no solution

[androm]

when i run my code i get this error message
"Failed to convert parameter value from a SqlParameter to a DateTime."

& i couldn't find what is wrong..... here's my code

 
protected void Button1_Click(object sender, EventArgs e)
    {
      SqlConnection thisConnection = new SqlConnection  
      (thisConnectionString);
        DataSet thisDataSet = new DataSet();
        thisConnection.Open();  
        DateTime from= new DateTime();
        DateTime to = new DateTime();
        from = DateTime.Parse(TextBox1.Text);
        to = DateTime.Parse(TextBox2.Text);
        ReportViewer1.Visible = true;
 
        SearchValue[0] = new SqlParameter 
           ("@datefrom",SqlDbType.DateTime);
        SearchValue[0].Value = from;
 
        SearchValue[1] = new SqlParameter("@dateto",
            SqlDbType.DateTime);
        SearchValue[1].Value = to;
 
        ReportViewer1.LocalReport.ReportPath 
           ="Report.rdlc";
 
        thisDataSet = SqlHelper.ExecuteDataset
      (thisConnection, "GetAllMissingItems",SearchValue);
 
        ReportDataSource datasource = new 
        ReportDataSource("BA2DataSet_GetAllMissingItems",
              thisDataSet.Tables[0]);
 
        ReportViewer1.LocalReport.DataSources.Clear();
        ReportViewer1.LocalReport.DataSources.Add
             (datasource);
        ReportViewer1.LocalReport.Refresh();
        }
 
 

and my 2 parameters in the stored proceduers are
@datefrom datetime, @dateto datetime

thx in advance