It's quite simple, you can create a stored procedure within SQL server and call the OPENROWSET method responsible for exporting data to a targeted  excel  sheet and you can pass the excel file as a parameter via the stored procedure
finally, you can call this procedure from within your C# code

This is the style of your SP

CREATE PROCEDURE ExportToExcel
(
    @filepath nvarchar(100), -- OK you can change from 100 to the numenr that  --fits  your needs
    @sheetname nvarchar(50)
)
INSERT INTO OPENROWSET('Microsoft.Jet.OLEDB.4.0',
'Excel 11.0;Database=C:\' + @filepath + ';',
'SELECT Name, Date FROM [' +@sheetname+ ']') SELECT * FROM yourdataTable
then you can call the stored procedure from within the C# code

string ConnectionString ="Integrated Security=SSPI;Initial Catalog=databasename;Data Source=servername;";
        SqlConnection conn = new SqlConnection(ConnectionString);

        SqlCommand StoredProcedureCommand = new SqlCommand("ExportToExcel", conn);
        StoredProcedureCommand.CommandType = CommandType.StoredProcedure;
        SqlParameter myParm1 = StoredProcedureCommand.Parameters.Add( "@filepath", SqlDbType.String); 
        myParm1.Value = @"C:\myfile.xlsx";
        SqlParameter myParm2 = StoredProcedureCommand.Parameters.Add("@sheetname", SqlDbType.String);
        myParm2.Value = "sheet$1";
        conn.Open();


       StoredProcedureCommand.excutenonequery;