VB语法

1、For循环

 For i As Integer = 0 To pTable.Fields.FieldCount - 1

    Next

2、Select语句

 Dim pFeatLyr As IFeatureLayer = pLayer
    Select pFeatLyr.FeatureClass.ShapeType
      Case ESRI.ArcGIS.Geometry.esriGeometryType.esriGeometryPoint : Return "Point"
      Case ESRI.ArcGIS.Geometry.esriGeometryType.esriGeometryPolygon : Return "Polygon"
      Case ESRI.ArcGIS.Geometry.esriGeometryType.esriGeometryPolyline : Return "Polyline"
    End Select

 3、自定义类

 Public Class RiverData
        Dim m_riverName As String
        Public Property RiverName
            Get
                Return m_riverName
            End Get
            Set(ByVal value)
                m_riverName = value
            End Set
        End Property
    End Class

 4、单利模式

  Public Shared Function Getinstance(ByVal AssetApplication As AssetApplication) As PropertyQueryFrom
    If PQfrom Is Nothing OrElse PQfrom.IsDisposed Then
      PQfrom = New PropertyQueryFrom
      PQfrom.m_AssetApplication = AssetApplication
    End If
    Return PQfrom
  End Function

 5、获取枚举的类型

enumPipeMaterial.钢管.GetType()

 6、计算时间差

  Private Function CoutTime(ByVal oldtime As DateTime, ByVal newtime As DateTime) As Integer
    Dim ts1 As TimeSpan = New TimeSpan(oldtime.Ticks)
    Dim ts2 As TimeSpan = New TimeSpan(newtime.Ticks)
    Dim ts3 As TimeSpan = ts1.Subtract(ts2).Duration()
    Return ts3.Days / 365
  End Function

 7、类型转换

TryCast(pLayer, IFeatureLayer) '转换失败返回Nothing
 CType(pLayer, IFeatureLayer)  '转换失败报错

 8、Linq 

     Dim query As IEnumerable(Of Data) = historyDataObj.Where(Function(x) x.DataID = dataId)
     For Each item As Data In query
     Next

  如果 historyDataObj 数组有Nothing 空值的话，上面的代码会出现问题，需要自定义函数判断，修改后的代码如下：

过滤的代码：

 Dim query As IEnumerable(Of RealData) = historyDataObj.Where(Function(x) CheakData(x, dataId))

过滤函数：

 Private Function CheakData(ByVal item As RealData, ByVal dataid As String) As Boolean
        If IsNothing(item) Then
            Return False
        Else
            Return item.DataID = dataid
        End If
    End Function

 

9、计算时差

    Private Function CoutTime(ByVal oldtime As DateTime) As String
        Dim ts1 As TimeSpan = New TimeSpan(oldtime.Ticks)
        Dim ts2 As TimeSpan = New TimeSpan(DateTime.Now.Ticks)
        Dim ts3 As TimeSpan = ts1.Subtract(ts2).Duration()
        Return ts3.Seconds & "秒" & ts3.Milliseconds & "毫秒"
    End Function

 10、生成txt并写入文本

     Dim str As StreamWriter = File.AppendText("e:\Alarmlog2.txt")
     str.WriteLine(Date.Now.ToString())
     str.Flush()
     str.Close()

 11、三目运算

Dim strResult As String
strResult = IIf(2 < 4, "yes", "no")

 12、定义一维数组

Dim ss(2) As Object