Mixed data type values can be read from excel file with the following Connection strings.
For Excel file below 2007 Version.
OleDbConnection Con = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + ExcelFilePath + @"; Extended Properties=Excel8.0;IMEX=1;HDR=NO;ImportMixedTypes=Text");
For Excel file 2007 and above Version.
OleDbConnection Con = new OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + ExcelFilePath + @"; Extended Properties=Excel12.0;IMEX=1;HDR=NO;ImportMixedTypes=Text");
IMEX=1
It means columns can have multiple datatype values.
HDR=NO
It means No header row.
ImportMixedTypes=Text
It means All mixed datatype columns will be treated as Text Type.