Getting error when I export datagridview data in excel in C#

Hello Guys, i am facing an issue and that is i want to export Datagridview data in excel and i have code am getting this code from here Export DataGridView To Excel In C#[^] Export DataGridView To Excel In C#[^] 
but the issue is when I export so it's saved automatically I want it's asking me where I want to save and second when it saves so I get this error 
Additional information: Exception from HRESULT: 0x800A03ECand one more thing I don't want to exit application after saving this file.
please help me guys, please.
Thank you.

Microsoft.Office.Interop.Excel._Application app = new Microsoft.Office.Interop.Excel.Application();
// creating new WorkBook within Excel application  
Microsoft.Office.Interop.Excel._Workbook workbook = app.Workbooks.Add(Type.Missing);
// creating new Excelsheet in workbook  
Microsoft.Office.Interop.Excel._Worksheet worksheet = null;
// see the excel sheet behind the program  
app.Visible = true;
// get the reference of first sheet. By default its name is Sheet1.  
// store its reference to worksheet  
worksheet = workbook.Sheets["Sheet1"];
worksheet = workbook.ActiveSheet;
// changing the name of active sheet  
worksheet.Name = "Exported from gridview";
// storing header part in Excel  
for (int i = 1; i < dataGridView4.Columns.Count+1; i++)
{
	worksheet.Cells[1, i] = dataGridView4.Columns[i - 1].HeaderText;
}
// storing Each row and column value to excel sheet  
for (int i = 0; i < dataGridView4.Rows.Count - 1; i++)
{
	for (int j = 0; j < dataGridView4.Columns.Count; j++)
	{
		worksheet.Cells[i + 2, j + 1] = dataGridView4.Rows[i].Cells[j].Value.ToString();
	}
}
// save the application  
workbook.SaveAs("Desktop:\\output.xls", Type.Missing);