「一つ以上の必要なパラメータに指定された値なし」という名前のパラメータをサポートしていません

Question

string Category = comboBox1.Text; 
string connectionString = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=C:\\Users\\admin\\Documents\\INV.xlsx; Extended Properties=\"Excel 8.0\""; 
OleDbConnection connection = new OleDbConnection(connectionString); 
string sql = "SELECT * FROM [RAW DATA$] WHERE [Category: Name] = @Category"; 
OleDbCommand cmd = new OleDbCommand(sql, connection); 
cmd.Parameters.AddWithValue("@num", SqlDbType.Int).Value = Category; 
OleDbDataAdapter dataadapter = new OleDbDataAdapter(sql, connection); 

Answer 1

のOleDbCommandは、このようmsdn documentation

変更CommandTextを見てみません：

string sql = "SELECT * FROM [RAW DATA$] WHERE [Category: Name] = ?";