OleDb Error: fill select command.connection property has not been initialized in ASP.Net

when run shows error as follows

fill selectcommand.connection property has not been initialized

how to fix this error. please let me know.

if (e.CommandName == "UploadFarmData")
{
string CurrentFilePath = Path.GetFullPath(FileUpload1.PostedFile.FileName);
constr = string.Format(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties=""Excel 12.0 Xml;HDR=YES;""", CurrentFilePath);
Econ = new OleDbConnection(constr);
Econ.Open();
DataTable dtExcelSchema;
dtExcelSchema = Econ.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null);
string sheetName = dtExcelSchema.Rows[0]["TABLE_NAME"].ToString();
DataSet ds = new DataSet();
string SheetName = dtExcelSchema.Rows[0]["TABLE_NAME"].ToString();
OleDbCommand cmdExcel = new OleDbCommand();
OleDbDataAdapter da = new OleDbDataAdapter();
cmdExcel.CommandText = "SELECT * From [" + SheetName + "]"; 
da.SelectCommand = cmdExcel;
da.Fill(ds);
Econ.Close();
DataTable dt = new DataTable();
dt = ds.Tables[0];
bool s = false;
if (dt.Rows.Count > 0)
{
for (int i = 0; i < dt.Rows.Count; i++)
{
dal.DAL_Insert_Farm_Data(dt.Rows[i]["Farmer Code"].ToString(), dt.Rows[i]["Farm No"].ToString(),
dt.Rows[i]["Type of Farm"].ToString(), dt.Rows[i]["Seeded Date"].ToString(), dt.Rows[i]["Farm Visit No"].ToString());
s = true;
}


if (s)
{
showStatusTrue.InnerHtml = "Farm Details Uploaded Successfully";
dal.DAL_Data_Update();
}