在Qt中选择串口（Linux）(Selecting serial port in Qt(Linux))

 for the SqlDataReader.GetString Method, No conversions are performed; therefore, the data retrieved must already be a string. 
 
 Call IsDBNull to check for null values before calling this method. 
 
 将您的代码更改为此，它应该工作 
 
cmdRoute.CommandText = "SELECT id, name FROM routes";
using (var rdrRoute = cmdRoute.ExecuteReader())
{
    if(rdrRoute.Read())
    {
        var route = new Route();
        route.Id  = rdrRoute["id"];
        if (!rdrRoute.IsDBNull(rdrRoute.GetOrdinal("name")))
        {
           route.Name = rdrRoute["name"].ToString();
           //route.Name = rdrRoute.GetString(rdrRount.GetOrdinal("name"));
           //may not work in .Net 4.0
        }
    }
}
 
 .NET 4.0 GetString（）可能会导致.NET 4.0中的错误/错误我会尝试将项目滚动到版本3.5或创建一个使用代码示例的项目并将其创建为.NET 3.5，如果这适用于GetString()我发现.net 4.0中存在一些错误，我不确定KB Fix何时发布 

for the SqlDataReader.GetString Method, No conversions are performed; therefore, the data retrieved must already be a string.
 
Call IsDBNull to check for null values before calling this method.
 
Change you code to this and it should work 
 
cmdRoute.CommandText = "SELECT id, name FROM routes";
using (var rdrRoute = cmdRoute.ExecuteReader())
{
    if(rdrRoute.Read())
    {
        var route = new Route();
        route.Id  = rdrRoute["id"];
        if (!rdrRoute.IsDBNull(rdrRoute.GetOrdinal("name")))
        {
           route.Name = rdrRoute["name"].ToString();
           //route.Name = rdrRoute.GetString(rdrRount.GetOrdinal("name"));
           //may not work in .Net 4.0
        }
    }
}
 
.NET 4.0 GetString() may cause errors / bugs in .NET 4.0 I would try rolling the project back to ver 3.5 or create a project that uses the code sample and create it as .NET 3.5, if this works with the GetString() I have found that there are some bugs in .net 4.0 and I am not sure when the KB Fix is going to release