I need a workaround for Excel Guessing Data Types problem

I found a solution by adding IMEX=1 for the connection string, but there's a special format for it which descriped in the following link.

The IMEX parameter is for columns that use mixed numeric and alpha values. The Excel driver will typically scan the first several rows in order to determine what data type to use for each column. If a column is determined to be numeric based upon a scan of the first several rows, then any rows with alpha characters in this column will be returned as Null. The IMEX parameter (1 is input mode) forces the data type of the column to text so that alphanumeric values are handled properly.

Regards

This isn't completely right! Apparently, Jet/ACE ALWAYS assumes a string type if the first 8 rows are blank, regardless of IMEX=1, and always uses a numeric type if the first 8 rows are numbers (again, regardless of IMEX=1). Even when I made the rows read to 0 in the registry, I still had the same problem. This was the only sure fire way to get it to work:

try
{
    Console.Write(wsReader.GetDouble(j).ToString());
}
catch   //Lame unfixable bug
{
    Console.Write(wsReader.GetString(j));
}

Can you work from the excel end? This example run in Excel will put mixed data tyoes into an SQL Server table:

Dim cn As New ADODB.Connection

scn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" _
& sFullName _
& ";Extended Properties=""Excel 8.0;HDR=Yes;IMEX=1"";"

cn.Open scn

s = "SELECT Col1, Col2, Col3 INTO [ODBC;Description=TEST;DRIVER=SQL Server;" _
& "SERVER=Some\Instance;Trusted_Connection=Yes;" _
& "DATABASE=test].TableZ  FROM [Sheet1$]"
cn.Execute s

An alternative solution is to add or change the setting TypeGuessRows in the registry. By setting its value to 0, the complete document will be scanned.

Unfortunately, the settings may be found on various locations in the registry, depending on the which libraries and versions of them you have installed.

For instance: [HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Jet\4.0\Engines\Excel] "TypeGuessRows"=dword:00000000

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\14.0\Access Connectivity Engine\Engines\Excel] "TypeGuessRows"=dword:00000000

This will also prevent truncation of textual data longer than 255 characters. This happens if you have a number for TypeGuessRows larger than 0 and the first text longer than 255 characters occurs beyond that number.

See also Setting TypeGuessRows for excel ACE Driver.