Question

 Try
   Dim conn As New MySql.Data.MySqlClient.MySqlConnection(myConnectionString)
   conn.Open()
   dbQuery = "select * from main_table"
   myCommand.CommandText = dbQuery
   myCommand.Connection = conn
   Dim myReader As MySqlDataReader
   myReader = myCommand.ExecuteReader()
   While myReader.Read()
      row_count = row_count + 1
   End While
   Catch ex As MySql.Data.MySqlClient.MySqlException
      MessageBox.Show(ex.Message)
   Finally
      conn.Close()
   End Try

   MessageBox.Show(row_count)
   conn.Close()

当我运行上面的代码时，它会显示正确的行数。但是，我试图一次将数据放入一个arraylist中。使用下面的代码不会给我一个错误，但它只读取第一行然后停止执行。

 Try
   Dim conn As New MySql.Data.MySqlClient.MySqlConnection(myConnectionString)
   conn.Open()
   dbQuery = "select * from main_table"
   myCommand.CommandText = dbQuery
   myCommand.Connection = conn
   Dim myReader As MySqlDataReader
   myReader = myCommand.ExecuteReader()
   While myReader.Read()
       For x As Integer = 0 To myReader.FieldCount
          col_array.Add(myReader.GetString(x))
       Next
   End While
   Catch ex As MySql.Data.MySqlClient.MySqlException
      MessageBox.Show(ex.Message)
   Finally
      conn.Close()
   End Try

   conn.Close()

我不明白为什么它会在读完第一行后停止。

Answer 1

评论如下：

从0到FieldCount的迭代将抛出IndexOutOfRangeException，它将在第一行之后中断。

For x As Integer = 0 To myReader.FieldCount
    col_array.Add(myReader.GetString(x))
Next

将其更改为myReader.FieldCount - 1结束以解决此问题。

如何将数据从MYSQL数据读取器获取到vb.net中的arraylist

1 个答案: