Asp.net 在dropdownlist中使用类增量运算符

我有一个名为

MonthDropDownList

的下拉列表，由sql数据源限定的月份组成。 现在我想访问

MonthDropDownList的值

MonthDropDownList.selecteditem++. 

所以

我怎样才能做到这一点

这是我的密码

DataClassesDataContext db = null;
    db = new DataClassesDataContext();
    tblAdvance advance = new tblAdvance();
    advance.StudentID = Convert.ToInt32(StudentNameDropDownList.SelectedValue);
    advance.FromMonth = FromMonthDropDownList.SelectedItem.Value;
    advance.UptoMonth = ToMonthDropDownList.SelectedItem.Value;
    advance.AdvanceAmount = Convert.ToInt32(txtAdvanceAmount.Text);
    advance.RollNo = Convert.ToInt32(txtRollNo.Text);
    db.tblAdvances.InsertOnSubmit(advance);
    db.SubmitChanges();
    db.Connection.Close();
    db.Dispose();
    for (int i = FromMonthDropDownList.SelectedIndex; i <= ToMonthDropDownList.SelectedIndex;i++ )
    {
     DataClassesDataContext dc = null;
     dc = new DataClassesDataContext();
     tblTotalFee bill = new tblTotalFee();
     bill.StudentID = Convert.ToInt32(StudentNameDropDownList.SelectedValue);

创建月数组

使用它的索引每月添加一次

string[] months = new string[] {"January", "February", "March", "April", "May",
         "June", "July", "August", "September", "October", "November", "December"};

假设您有一个id为dd1的
dropdownlist
，值为
0,1,2，…

如果您需要查找
二月
，并且您有值
1
，则可以这样做

int current month=1;
string nextmonth=months[current+1];

好的，如果您有两个下拉列表，在几个月内充当上限和下限，那么SelectedValue++函数将如下所示（VB.NET）：

这将返回列表中的下一个月，除非“下限”列表中的月份等于或大于“上限”列表中的月份，在这种情况下，它只返回上限月份

这就是你的意思，还是你需要递归的东西？
我用这段代码找到了答案。这很简单，但可能是我觉得问题太复杂了

 DataClassesDataContext db = null;
    db = new DataClassesDataContext();
    tblAdvance advance = new tblAdvance();
    advance.StudentID = Convert.ToInt32(StudentNameDropDownList.SelectedValue);
    advance.FromMonth = FromMonthDropDownList.SelectedItem.Value;
    advance.UptoMonth = ToMonthDropDownList.SelectedItem.Value;
    advance.AdvanceAmount = Convert.ToInt32(txtAdvanceAmount.Text);
    advance.RollNo = Convert.ToInt32(txtRollNo.Text);
    db.tblAdvances.InsertOnSubmit(advance);
    db.SubmitChanges();
    db.Connection.Close();
    db.Dispose();
    int k = FromMonthDropDownList.SelectedIndex;
    int l = ToMonthDropDownList.SelectedIndex;
    for (int i = k; i <= l;i++ )
    {
        DataClassesDataContext dc = null;
        dc = new DataClassesDataContext();
        tblTotalFee bill = new tblTotalFee();
        bill.StudentID = Convert.ToInt32(StudentNameDropDownList.SelectedValue);
        bill.MonthName = FromMonthDropDownList.SelectedItem.Value;
        bill.DueFromPreviousMonth = 0;
        bill.ECAFee = 0;
        bill.HostelFee = 0;
        bill.LateFeeCharges = 0;
        bill.MonthlyFee = 0;
        bill.TransportFee = 0;
        bill.TotalFeeThisMonthAlongwithDueinthismonth=0;
        FromMonthDropDownList.SelectedIndex++;
        dc.tblTotalFees.InsertOnSubmit(bill);
        dc.SubmitChanges();
        dc.Connection.Close();
        dc.Dispose();
        }
}

DataClassesDataContext db=null；
db=新的DataClassesDataContext（）；
tblAdvance advance=新的tblAdvance（）；
advance.StudentID=Convert.ToInt32（StudentNameDropDownList.SelectedValue）；
advance.FromMonth=FromMonthDropDownList.SelectedItem.Value；
advance.UptoMonth=tomonthropdownlist.SelectedItem.Value；
advance.AdvanceAmount=Convert.ToInt32（txtdvanceamount.Text）；
advance.RollNo=Convert.ToInt32（txtRollNo.Text）；
db.tblAdvances.INSERTONSUPMIT（预付款）；
db.SubmitChanges（）；
db.Connection.Close（）；
db.Dispose（）；
int k=FromMonthDropDownList.SelectedIndex；
int l=ToMonthDropDownList.SelectedIndex；
对于（int i=k；简单地说，我有两个下拉列表，上面的月份和下面的月份。然后我有一个循环，如果我把上面的月份放在一月，下面的月份放在三月，那么上面的月份++应该是二月，上面的月份++必须暗示marchIn简单的单词，上面的月份和下面的月份是两个下拉列表。然后我有一个循环其中，如果我把上个月放在一月，下个月放在三月，那么上个月++应该是二月，上个月++必须是三月…这是我的实际需求@Shekhar
int current month=1;
string nextmonth=months[current+1];

Public Function GetNextMonth(ByVal dd1 as DropDownList, Byval dd2 as DropDownList) as String
     If dd1.Items(dd1.SelectedIndex + 1).SelectedValue >= dd2.SelectedValue then
            Return dd2.SelectedItem.Text
     else
            Return dd1.Items(dd1.SelectedIndex + 1).Text
     end if
End Sub

 DataClassesDataContext db = null;
    db = new DataClassesDataContext();
    tblAdvance advance = new tblAdvance();
    advance.StudentID = Convert.ToInt32(StudentNameDropDownList.SelectedValue);
    advance.FromMonth = FromMonthDropDownList.SelectedItem.Value;
    advance.UptoMonth = ToMonthDropDownList.SelectedItem.Value;
    advance.AdvanceAmount = Convert.ToInt32(txtAdvanceAmount.Text);
    advance.RollNo = Convert.ToInt32(txtRollNo.Text);
    db.tblAdvances.InsertOnSubmit(advance);
    db.SubmitChanges();
    db.Connection.Close();
    db.Dispose();
    int k = FromMonthDropDownList.SelectedIndex;
    int l = ToMonthDropDownList.SelectedIndex;
    for (int i = k; i <= l;i++ )
    {
        DataClassesDataContext dc = null;
        dc = new DataClassesDataContext();
        tblTotalFee bill = new tblTotalFee();
        bill.StudentID = Convert.ToInt32(StudentNameDropDownList.SelectedValue);
        bill.MonthName = FromMonthDropDownList.SelectedItem.Value;
        bill.DueFromPreviousMonth = 0;
        bill.ECAFee = 0;
        bill.HostelFee = 0;
        bill.LateFeeCharges = 0;
        bill.MonthlyFee = 0;
        bill.TransportFee = 0;
        bill.TotalFeeThisMonthAlongwithDueinthismonth=0;
        FromMonthDropDownList.SelectedIndex++;
        dc.tblTotalFees.InsertOnSubmit(bill);
        dc.SubmitChanges();
        dc.Connection.Close();
        dc.Dispose();
        }
}