使用c#无法将获取错误字符串识别为有效

Question

当我试图改变日期格式从csv文件3/1/2021-3/31/2021到3月-01-2021-3月-31-2021获得错误，请帮助我解决这个问题。

                       foreach (DataRow dr in dtDataTable.Rows)
        {
            for (int i = 0; i < dtDataTable.Columns.Count; i++)
            {
                if (ListInputDateColumns.Contains(dtDataTable.Columns[i].ColumnName))
                {
                    if(dtDataTable.Columns[i].ColumnName == "Period")
                    {
                        sw.Write(dr[i] = Convert.ToDateTime(dtDataTable.Rows[i][dtDataTable.Columns[i].ColumnName.ToString()]).ToString("MMM-dd-yyyy-MMM-dd-yyyy"));//Here i am getting error
                    }
                    else
                    {
                        sw.Write(dr[i] = Convert.ToDateTime(dtDataTable.Rows[i][dtDataTable.Columns[i].ColumnName.ToString()]).ToString("MMM-dd-yyyy hh:mm:ss tt"));
                    }
                    //sw.Write(dr[i].ToString());
                }
                else
                {
                    sw.Write(dr[i].ToString());
                }
                //sw.Write(dr[i].ToString());
                sw.Write(",");
            }
            sw.Write(sw.NewLine);
        }
        sw.Close();
    }
}

Answer 1

您必须解析该字符串，将其拆分为分隔符，然后将每个令牌解析为DateTime。然后，您可以将其转换为具有所需格式的字符串：

string targetFormat = "MMM-dd-yyyy";
string s = " 3/1/2021-3/31/2021";
string[] tokens = s.Split('-');
if(tokens.Length == 2)
{
    bool validFrom = DateTime.TryParse(tokens[0], CultureInfo.InvariantCulture, DateTimeStyles.None, out DateTime fromDate);
    bool validTo = DateTime.TryParse(tokens[1], CultureInfo.InvariantCulture, DateTimeStyles.None, out DateTime toDate);
    if (validFrom && validTo)
    {
        string result = $"{fromDate.ToString(targetFormat, CultureInfo.InvariantCulture)}-{toDate.ToString(targetFormat, CultureInfo.InvariantCulture)}";           
    }
}

Answer 2

好的，如果你愿意的话，我们可以用一行代码来做这件事，但就可读性而言，它会变得很难看。对于一个班轮，只需更改这一行：

sw.Write(dr[i] = Convert.ToDateTime(dtDataTable.Rows[i][dtDataTable.Columns[i].ColumnName.ToString()]).ToString("MMM-dd-yyyy-MMM-dd-yyyy"));//Here i am getting error

至

sw.Write(dr[i] = Convert.ToDateTime((dtDataTable.Rows[i][dtDataTable.Columns[i].ColumnName.ToString()]).Substring(0, (dtDataTable.Rows[i][dtDataTable.Columns[i].ColumnName.ToString()]).IndexOf('-'))).ToString("MMM-dd-yyyy") + "-" + Convert.ToDateTime((dtDataTable.Rows[i][dtDataTable.Columns[i].ColumnName.ToString()]).Substring((dtDataTable.Rows[i][dtDataTable.Columns[i].ColumnName.ToString()]).IndexOf('-') + 1)).ToString("MMM-dd-yyyy");

但是对于可维护性，我建议创建一个快速的方法来解析“周期”，如下所示

string ParsePeriod(string period)

{

DateTime from = Convert.ToDateTime(period.Substring(0, period.IndexOf('-')));

DateTime to = Convert.ToDateTime(period.Substring(period.IndexOf('-') + 1));

return from.ToString("MMM-dd-yyyy") + "-" + to.ToString("MMM-dd-yyyy");

}

然后用这样的方式来称呼它：

sw.Write(dr[i] = Convert.ToDateTime(dtDataTable.Rows[i][dtDataTable.Columns[i].ColumnName.ToString()]).ToString("MMM-dd-yyyy-MMM-dd-yyyy"));//Here i am getting error

对此：

sw.Write(dr[i] = ParsePeriod(Convert.ToString(dtDataTable.Rows[i][dtDataTable.Columns[i].ColumnName.ToString()])));

我相信这能解决你的问题。;-)