OleDbConnection con = new OleDbConnection(
@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source="
+ _xlsFilePath + ";Extended Properties=\"Excel 8.0;HDR=YES;IMEX=1\";");
OleDbDataAdapter da = new OleDbDataAdapter
("select * from [" + sheetName + "$]", con);
DataTable dt = new DataTable();
da.MissingSchemaAction = MissingSchemaAction.AddWithKey;
da.FillSchema(dt, SchemaType.Source);
da.Fill(dt);
return dt;

We tried various options in the connection strings but nothing worked. Later we found this MS Support article, which helps to resolve this error using Registry Editing. This issue is because the Jet Engine reads the first 8 cells of each column and check it’s data type.

You can fix this problem by setting a value between 0 to 16 for the TypeGuessRows key in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Jet\4.0\Engines\Excel location. If you put 0 as the value, Jet engine will read the first 16000 rows, which may affect the performance.

You can resolve this problem with code.

RegistryKey key = Registry.LocalMachine.OpenSubKey(
@"SOFTWARE\Microsoft\Jet\4.0\Engines\Excel\", true);
if (null != key)
{
key.SetValue("TypeGuessRows", 0, RegistryValueKind.DWord);
}

string connectionString = "Provider=Microsoft.Jet.OleDb.4.0; Data Source=C:\Sample.xls; Extended Properties=Excel 8.0;"

Please note the “Extended Properties” attribute. This attribute helps us to query the excel file.

Exporting Data from Data Table to Excel File.

string connectionString = "Provider=Microsoft.Jet.OleDb.4.0; Data Source=C:\Sample.xls; Extended Properties=Excel 8.0;"
// Establish a connection to the data source.
using(OleDbConnection Connection = new OleDbConnection(connectionString))
{
Connection.Open()
//creating a new Sheet with name sample and three columns with Heading firstname, lastname and email
using(OleDbCommand command = new OleDbCommand())
{
command.Connection = Connection;
command.CommandText = "CREATE TABLE [Sample$](FirstName Char(255), LastName char(255), Email char(255))";
command.ExecuteNonQuery();
}
//Adding records to the Sample Worksheet
using(OleDbCommand command = new OleDbCommand())
{
command.Connection = Connection;
command.CommandText = "INSERT INTO TABLE [Sample$](FirstName,LastName,Email) VALUES('Anuraj','P','anuraj.p@example.com')";
command.ExecuteNonQuery();
command.CommandText = "INSERT INTO TABLE [Sample$](FirstName,LastName,Email) VALUES('sreekumar','vn','sreekumar.vn@example.com')";
command.ExecuteNonQuery();
}
}

Import the Data from Excel

DataTable dt;
string connectionString = "Provider=Microsoft.Jet.OleDb.4.0; Data Source=C:\Sample.xls; Extended Properties=Excel 8.0;"
// Establish a connection to the data source.
using(OleDbConnection Connection = new OleDbConnection(connectionString))
{
Connection.Open()
//reading data from excel to Data Table
using(OleDbCommand command = new OleDbCommand())
{
command.Connection = Connection;
command.CommandText = "SELECT * FROM [Sample]";
using(OleDbDataAdapter adapter =new OleDbDataAdapter())
{
adapter.SelectCommand = command;
adapter.Fill(dt);
}
}
}

You can get more information from Microsoft support site

http://support.microsoft.com/kb/306023 – How to transfer data to an Excel workbook by using Visual C# 2005 or Visual C# .NET