[VB.NET]大家看看，这段代码出错了，要怎么改，谢谢，，在线等，当天结贴！！！！！！

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大家看看，这段代码出错了，要怎么改，谢谢，，在线等，当天结贴！！！！！！
Private Sub addnewitem()
Dim nowTable As DataTable = New DataTable( nowCartTable )
nowTable = Session( myCartTable )
Dim data As DataSet
With New BusinessRule.Ecom

data = .GetPro(ID.Text)

End With

Dim newDR As DataRow

newDR = nowTable.NewRow


newDR.Item(0) = ID.Text
newDR.Item(1) = data.Tables(0).Rows(0).Item(2)
newDR.Item(2) = data.Tables(0).Rows(0).Item(5)
newDR.Item(3) = 1
newDR.Item(4) = newDR.Item(2)
nowTable.Rows.Add(newDR)

Session( myCartTable ) = nowTable

End Sub
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Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:


Line 147: Dim newDR As DataRow
Line 148:
Line 149: newDR = nowTable.NewRow
Line 150:
Line 151:

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nowTable = Session( myCartTable )??
Session是不是一个空值？
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http://msdn2.microsoft.com/zh-cn/library/system.data.datatable.newrow(VS.80).aspx
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Session( myCartTable ) 的值为空

Dim nowTable As DataTable
nowTable =(DataTable)Session( myCartTable )
if(nowTable is not nothing)
{
...........................
}
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应该是这行出错吧： newDR = nowTable.NewRow
是nowTable为空时出错，这里应该加判断，当Session( myCartTable )
为空时，如何作，否则你第一次运行肯定会为空，那你这个代码一定会抛这个异常
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