The type or namespace name 'Interop' does not exist in the n

Question

 Error Show like this when 

 

export databse to excel file

 

 

"The type or namespace name 'Interop' does not exist in the namespace 'Microsoft.Office' (are you missing an assembly reference?"

 

 

if (dataGridView.Rows.Count > 0)
{
Microsoft.Office.Interop.Excel.ApplicationClass XcelApp = new Microsoft.Office.Interop.Excel.ApplicationClass();
XcelApp.Application.Workbooks.Add(Type.Missing);

for (int i = 1; i < dataGridView.Columns.Count + 1; i++)
{
XcelApp.Cells[1, i] = dataGridView.Columns[i - 1].HeaderText;
}

for (int i = 0; i < dataGridView.Rows.Count; i++)
{
for (int j = 0; j < dataGridView.Columns.Count; j++)
{
XcelApp.Cells[i + 2, j + 1] = dataGridView.Rows[i].Cells[j].Value.ToString();
}
}
XcelApp.Columns.AutoFit();
XcelApp.Visible = true;
}