How to Insert data in Excel file using C#? thks in advance..

You can easily add row to Excel using ADO.NET

string fileName = @"D:\demo.xlsx"; 
string connectionString = String.Format(@"Provider=Microsoft.ACE.OLEDB.12.0;" + 
        "Data Source={0};Extended Properties='Excel 12.0;HDR=YES;IMEX=0'", fileName); 

using(OleDbConnection cn = new OleDbConnection(connectionString))
{
    cn.Open();
    OleDbCommand cmd1 = new OleDbCommand("INSERT INTO [Sheet1$] " + 
         "([Column1],[Column2],[Column3],[Column4]) " + 
         "VALUES(@value1, @value2, @value3, @value4)", cn);
   cmd1.Parameters.AddWithValue("@value1", "Name");
   cmd1.Parameters.AddWithValue("@value2", "Address");
   cmd1.Parameters.AddWithValue("@value3", PhoneNumber);
   cmd1.Parameters.AddWithValue("@value4", PinCode);
   cmd1.ExecuteNonQuery();
}

Assuming that, you have a first row with an header with Column1... as column names. Also, the code use the ACE OleDB provider for Excel 2007 or 2010 instead of Microsoft.Jet.OleDb.4.0.