Vb.net 如何从SQLite表中获取值的总和？

我试图从一个专栏中收集出价并分发平均值

    Try
        TotalSum += Convert.ToInt32(row(Column))
        Console.WriteLine("Calculating TotalSum {0}", TotalSum.ToString)
    Catch
    End Try

我收到一个InvalidCast异常：指定的强制转换无效。论总和+=

    Try
        TotalSum += Convert.ToInt32(row(Column))
        Console.WriteLine("Calculating TotalSum {0}", TotalSum.ToString)
    Catch
    End Try

任何帮助都将不胜感激

Dim sql As String = "SELECT " & Column & " FROM " & Table & " ;"
Dim dt As DataTable = SQLiteDatabase.GetDataTable(sql)
Column = Column.Replace("[", "")
Column = Column.Replace("]", "")
For Each row As DataRow In dt.Rows
    TotalSum += DirectCast(row(Column), Integer)
    Console.WriteLine("Calculating TotalSum {0}", TotalSum.ToString)
Next row

    Try
        TotalSum += Convert.ToInt32(row(Column))
        Console.WriteLine("Calculating TotalSum {0}", TotalSum.ToString)
    Catch
    End Try

检查这个

int suma = 0;

Dim dc as DataColumn = dt.Columns[0]  //Column to add
For Each row As DataRow In dt.Rows
          suma += int.Parse(row[dc])

    Try
        TotalSum += Convert.ToInt32(row(Column))
        Console.WriteLine("Calculating TotalSum {0}", TotalSum.ToString)
    Catch
    End Try

---

您好

谢谢您的回复

    Try
        TotalSum += Convert.ToInt32(row(Column))
        Console.WriteLine("Calculating TotalSum {0}", TotalSum.ToString)
    Catch
    End Try

我的解决办法是

    Try
        TotalSum += Convert.ToInt32(row(Column))
        Console.WriteLine("Calculating TotalSum {0}", TotalSum.ToString)
    Catch
    End Try

---

尝试添加Catch块以监视vbNull。我只想要大于0的值，最终的解决方案是

    Try
        TotalSum += Convert.ToInt32(row(Column))
        Console.WriteLine("Calculating TotalSum {0}", TotalSum.ToString)
    Catch
    End Try

Dim suma As Double = 0.0R
For Each row As DataRow In dt.Rows
    Dim num As Double = 0R
    Double.TryParse(row(Column).ToString, num)
    suma += num
Next row

---

在我的应用程序中，列可能包含Stings，因为用户可以直接输入SQL。我只使用双精度类型，但整数是一个选项

1。你的总和是整数吗？2.检查dt中的每一行，确保列是整数列。在第一行有一个dbNull。它不在表中是的，这就是错误的来源。您可以放置一个try-catch块来跳过该记录，就像您的答案一样，但是检查空值的原因会更好。

    Try
        TotalSum += Convert.ToInt32(row(Column))
        Console.WriteLine("Calculating TotalSum {0}", TotalSum.ToString)
    Catch
    End Try