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我遇到了返回类型“T”值的麻烦。这是更容易显示,而不是解释所以这里是方法:从函数返回一个通用函数类型的值
Protected Function GetElementValue(Of T)(ByVal nodeName As String, Optional missingIfNotExists As Boolean = True,
Optional missingIfEmpty As Boolean = True,
Optional ByRef defaultVal As T = Nothing,
Optional maxLength As Integer = Nothing) As T
'Set up the node to get the value from
Dim node = xmlRoot.SelectSingleNode(nodeName)
Select Case True
Case IsNothing(node) 'If the node is missing from the xml document
'Add the node to the misssing elements array if missingIfNotExists = True
If missingIfNotExists Then missingElements.Add(nodeName)
'Return the default value
Return defaultVal
Case node.InnerText.Trim.Length = 0 'The node exists in the xml document but has no value
'Add it to missing elements if missingIfEmpty = True
If missingIfEmpty Then missingElements.Add(nodeName)
'If there is a default value passed in, return that value
Return defaultVal
Case Else 'The node exists and contains data
End Select
'The element exists and contains data
Dim nodeValue = node.InnerText.Trim
'If a size constraint was passed in, ensure the element data is not too long. Shorten the string if it is
If Not IsNothing(maxLength) AndAlso nodeValue.Length > maxLength Then nodeValue = nodeValue.Substring(0, maxLength)
Return CType(nodeValue, T)
End Function
任何想法或建议?
谢谢。
最后的回报是我遇到问题的地方。它说“的nodeValue不能被转换为T类型”
我曾尝试下面的场景,我得到的错误:“整型的值不能coverted键入T”:
Select Case defaultVal.GetType()
Case GetType(Integer)
Return CType(nodeValue, Integer)
End Select