Your code line is looking pretty good. Try to add @ before the string or add back slash like this \\\\" + PCName
string myconnectionstring = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=\\\\" + PCName + "\\datafolder\\data.mdb";
If still it creates problem then assign that database shared folder as a Mapped Drive and use something like this. for example mapped drive is Z: (\\PCName\ApplicationFolder)
string myconnectionstring = @"Provider=Microsoft.Jet.OLEDB.4.0; Data Source=Z:\datafolder\data.mdb";
also this solution does not working then the problem may be in network pc permission.