无法隐式转换类型'int?'到"int". [英] Cannot implicitly convert type 'int?' to 'int'.

问题描述

我收到错误消息无法隐式转换类型'int?'到'int'.在返回行上我的OrdersPerHour上存在显式转换(您是否需要强制转换?).我不知道为什么，因为我的C#技能没有那么先进.任何帮助将不胜感激.

I'm getting the error "Cannot implicitly convert type 'int?' to 'int'. An explicit conversion exists (are you missing a cast?)" on my OrdersPerHour at the return line. I'm not sure why because my C# skills are not that advanced. Any help would be appreciated.

static int OrdersPerHour(string User)
{
    int? OrdersPerHour;
    OleDbConnection conn = new OleDbConnection(strAccessConn);
    DateTime curTime = DateTime.Now;        

    try
    {
        string query = "SELECT COUNT(ControlNumber) FROM Log WHERE DateChanged > #" + curTime.AddHours(-1) + "# AND User = '" + User + "' AND Log.EndStatus in ('Needs Review', 'Check Search', 'Vision Delivery', 'CA Review', '1TSI To Be Delivered');";
        OleDbCommand dbcommand = new OleDbCommand(query, conn);
        dbcommand.Connection.Open();
        dbcommand.CommandType = CommandType.Text;
        OrdersPerHour = (int?)dbcommand.ExecuteScalar();

        Console.WriteLine("Orders per hour for " + User + " is " + OrdersPerHour);            
    }
    catch (OleDbException ex)
    {

    }
    finally
    {
        conn.Close();
    }
    return OrdersPerHour;
}

推荐答案

好吧，您要将 OrdersPerHour 强制转换为 int?

Well you're casting OrdersPerHour to an int?

OrdersPerHour = (int?)dbcommand.ExecuteScalar();

但是您的方法签名是 int :

static int OrdersPerHour(string User)

这两个必须匹配.

还有一个快速建议-> 在查询中使用参数，例如:

Also a quick suggestion -> Use parameters in your query, something like:

string query = "SELECT COUNT(ControlNumber) FROM Log WHERE DateChanged > ? AND User = ? AND Log.EndStatus in ('Needs Review', 'Check Search', 'Vision Delivery', 'CA Review', '1TSI To Be Delivered')";
OleDbCommand dbcommand = new OleDbCommand(query, conn);
dbcommand.Parameters.Add(curTime.AddHours(-1));
dbcommand.Parameters.Add(User);

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