Check null and emptry string in a cell while retrieving the excel data
<p>Error : Additional information: Syntax error (missing operator) in query expression '[SKU N#] !='''.</p>

<pre><code> if (getFileExtension.ToLower() == ".xls")
                            {
                                conString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + getFileName + ";Extended Properties=\"Excel 8.0;HDR=Yes;;IMEX=1\""; ;
                            }
                            else if (getFileExtension.ToLower() == ".xlsx")
                            {
                                conString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + getFileName + ";Extended Properties=\"Excel 12.0;HDR=Yes;;IMEX=1\"";
                            }
                            OleDbConnection con = new OleDbConnection(conString);
                            if (con.State == ConnectionState.Closed) con.Open();
                            System.Data.DataTable ExcelSheets = con.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, new object[] { null, null, null, "TABLE" });
                            string SpreadSheetName = ExcelSheets.Rows[0]["TABLE_NAME"].ToString();

                            switch (UpdateProductViewModel.ProductDataType)
                            {
                                case 1:
                                    query = "SELECT * FROM [" + SpreadSheetName + "] WHERE [SKU N#] !='' AND [SKU N#] NOT LIKE '%P'";
                                    break;
                                case 2:
                                    query = "SELECT * FROM [" + SpreadSheetName + "] WHERE [SKU N#] !='' AND [SKU N#] LIKE '%P'";
                                    break;
                                case 3:
                                    query = "SELECT * FROM [" + SpreadSheetName + "] WHERE [SKU N#] !=''";
                                    break;
                            }
</code></pre>

<p>When I remove the <strong>WHERE [SKU N#] !=''</strong> this line from where it works fine. what I am doing wrong here ? </p>