When create Excel file using c# cannot open it

I try to create excel file using c# windows form visual studio 2015

i need to create excel file with excel 2007 with extension xlsx

after i click the button and got to path i need to create i found file in path

But cannot open it .

my code as bellow:

Code:

---

public void CreateSheetIfNotExists() 
      { 
          using (System.Data.OleDb.OleDbConnection databaseConnection = new System.Data.OleDb.OleDbConnection()) 
          { 
 
              DataTable schemaTable = default(DataTable); 
 
              databaseConnection.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;" + "Data Source=D:\\Book310.xlsx;Extended Properties=Excel 12.0;"; 
 
              databaseConnection.Open(); 
 
              schemaTable = databaseConnection.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Tables, new object[] { 
          null, 
          null, 
          "Sheet1$" 
      }); 
 
              if (schemaTable.Rows.Count == 0) 
              { 
                  string SQLDDLCommand = "CREATE TABLE [Sheet1] (UserID INTEGER, UserName CHAR(255))"; 
                  System.Data.OleDb.OleDbCommand excelCommand = new System.Data.OleDb.OleDbCommand(SQLDDLCommand, databaseConnection); 
                  excelCommand.ExecuteNonQuery(); 
                   
              } 
             
              databaseConnection.Close(); 
          } 
      }

---

after that file 310 created but not open
when open file i get this error
excel cannot open the file because the file format or file extension is not valid. verify that the file has not been corrupted and that the file extention matches the format of the file."
How to solve this problem if possible ?

Rather than create a new file each time, create a folder below the app folder, place a blank Excel file there. When needed copy it to the app folder and use it. I've done this in the follow code sample.