问题：从字符串转换日期和/或时间时转换失败

Question

我想根据当月获取购买总额，但是在我的 SQL 服务器数据库中，我将日期字段设置为写入 nvarchar(50)。 执行代码时，出现错误：

从字符串转换日期和/或时间时转换失败。

有没有办法更改代码以使其接受 nvarchar(50) 字段类型，但我不想将其从数据库更改为日期类型，我希望它适用于 nvarchar(50) 类型。

代码：

int month = Convert.ToInt32(DateTime.Now.Month.ToString());
DataTable tblItems_40 = new DataTable();
tblItems_40 = db8.readData("SELECT  SUM(Total) FROM Buy_Detalis WHERE MONTH(Date) 
         ='" + month + "' ", "");
tblItems8 = db8.readData("SELECT * From Buy_Detalis WHERE Date ='" + 
         month.ToString() + "'", "");
if (tblItems8.Rows.Count <= 0)
{
    labelControl6.Text = "0.ج.م";
}
else if (tblItems8.Rows.Count >= 1)
{
    labelControl6.Text = (tblItems_40.Rows[0][0].ToString)();
    labelControl6.Text = Decimal.Parse(labelControl6.Text).ToString("C");
}

Answer 1

我想出了这个解决方案并想与您分享它对我来说非常有用

DataTable tblItems_40 = new DataTable();
        string d5 = DateTime.Now.Month.ToString();
        string d6 = DateTime.Now.Year.ToString();
        tblItems_40 = db4.readData("SELECT YEAR(CONVERT(date,[Buy_Detalis].[Date], 103)) as SalesYear,MONTH(CONVERT(date,[Buy_Detalis].[Date], 103)) as SalesMonth,sum(Buy_Detalis.Total) AS TotalSales FROM Buy_Detalis where YEAR(CONVERT(date,[Buy_Detalis].[Date], 103)) ='" + d6 + "' AND MONTH(CONVERT(date,[Buy_Detalis].[Date], 103)) ='" + d5+ "'  GROUP BY YEAR(CONVERT(date,[Buy_Detalis].[Date], 103)), MONTH(CONVERT(date,[Buy_Detalis].[Date], 103))  ", "");
        tblItems8 = db4.readData("SELECT sum(Buy_Detalis.Total) AS TotalSales FROM Buy_Detalis GROUP BY YEAR(CONVERT(date,[Buy_Detalis].[Date], 103)), MONTH(CONVERT(date,[Buy_Detalis].[Date], 103)) ORDER BY YEAR(CONVERT(date,[Buy_Detalis].[Date], 103)), MONTH(CONVERT(date,[Buy_Detalis].[Date], 103))", "");
        if (tblItems8.Rows.Count <= 0)
        {
            labelControl6.Text = "0.ج.م";
        }
        if (tblItems8.Rows.Count >= 1)
        {
            labelControl6.Text = (tblItems_40.Rows[0][2].ToString)();
            labelControl6.Text = Decimal.Parse(labelControl6.Text).ToString("C");
        }