在c#中打开与Mysql的连接时，对象无法从DBNull转换为其他类型

Question

Line 27:             try
Line 28:             {
Line 29:                 Conn.Open();
Line 30:                 MySqlReader = cmd.ExecuteReader();
Line 31:                 if (MySqlReader.Read() == true)

我尝试更改 Mysql.dll 并添加对 Web 配置的引用，但没有成功。我在打开连接时遇到错误

'Line 29:                 Conn.Open();'

Answer 1

以下是排查和解决问题的一些步骤：

读取数据时检查DBNull

int value = MySqlReader.IsDBNull(columnIndex) ? defaultValue : MySqlReader.GetInt32(columnIndex);

try
{
    Conn.Open();
    MySqlReader = cmd.ExecuteReader();
    while (MySqlReader.Read())
    {
        // Example of reading an integer, with a check for DBNull
        int someColumnValue = MySqlReader.IsDBNull(columnIndex) ? 0 : MySqlReader.GetInt32(columnIndex);
        // Process other columns similarly
    }
}
catch (Exception ex)

{

// Log the exception details for debugging
Console.WriteLine(ex.Message);

}
finally
{
    // Close the reader and connection if open
    MySqlReader?.Close();
    Conn?.Close();

}