Question

我是VB.Net的新手。我正在尝试调试我的项目，但我收到一个警告：变量＆csCryptoStream＆＃39;在被赋值之前使用。在运行时

可能会导致空引用异常

我该如何解决？

Private Sub EncryptOrDecryptFile(strInputFile As String, strOutputFile As String, bytKey As Byte(), bytIV As Byte(), Direction As crypt.CryptoAction)
    ' The following expression was wrapped in a checked-statement
    Try
        Me.fsInput = New FileStream(strInputFile, FileMode.Open, FileAccess.Read)
        Me.fsOutput = New FileStream(strOutputFile, FileMode.OpenOrCreate, FileAccess.Write)
        Me.fsOutput.SetLength(0L)
        Dim bytBuffer As Byte() = New Byte(4096) {}
        Dim lngBytesProcessed As Long = 0L
        Dim lngFileLength As Long = Me.fsInput.Length
        Dim cspRijndael As RijndaelManaged = New RijndaelManaged()
        Me.pbStatus.Value = 0
        Me.pbStatus.Maximum = 100
        Dim csCryptoStream As CryptoStream
        Select Case Direction
            Case crypt.CryptoAction.ActionEncrypt
                csCryptoStream = New CryptoStream(Me.fsOutput, cspRijndael.CreateEncryptor(bytKey, bytIV), CryptoStreamMode.Write)
            Case crypt.CryptoAction.ActionDecrypt
                csCryptoStream = New CryptoStream(Me.fsOutput, cspRijndael.CreateDecryptor(bytKey, bytIV), CryptoStreamMode.Write)
        End Select
        While lngBytesProcessed < lngFileLength
            Dim intBytesInCurrentBlock As Integer = Me.fsInput.Read(bytBuffer, 0, 4096)

Warning --->     csCryptoStream.Write(bytBuffer, 0, intBytesInCurrentBlock)
            ' The following expression was wrapped in a unchecked-expression
            lngBytesProcessed += CLng(intBytesInCurrentBlock)
            ' The following expression was wrapped in a unchecked-expression
            Me.pbStatus.Value = CInt(Math.Round(CDec(lngBytesProcessed) / CDec(lngFileLength) * 100.0))
        End While

Answer 1

声明df=read.csv("https://dl.dropboxusercontent.com/u/6791606/Flagellum%20track%200012%20100fps%20-%20converted.csv",header=T) start_x=c() start_y=c() slice_id=c() angle=c() for(i in 1:length(unique(df$Slice))) { sl = df[df$Slice==unique(df$Slice)[i],] slice_id = unique(df$Slice)[i] start_x[i] = sl[1,2] start_y[i] = sl[1,3] angle[i] = -atan((sl[1,3]-tail(sl,1)[,3])/(sl[1,2]-tail(sl,1)[,2])) } gl_mean_x = mean(start_x) gl_mean_y = mean(start_y) gl_mean_angle = mean(angle) df$X_center = df$X-gl_mean_x df$Y_center = df$Y-gl_mean_y ## compute mean angle / create new score alpha = gl_mean_angle rotm <- matrix(c(cos(alpha),sin(alpha),-sin(alpha),cos(alpha)),ncol=2) M = cbind(df$X_center,df$Y_center) M2 <- t(rotm %*% ( t(M)-c(M[1,1],M[1,2]) )+c(M[1,1],M[1,2])) df$X_center_angle = M2[,1] df$Y_center_angle = M2[,2] library(ggplot2) ggplot(df, aes(x = X_center_angle, y = Y_center_angle)) + geom_line(aes(color = factor(Slice))) + stat_smooth(aes(color = factor(Slice)), se = FALSE)如下：
```
CryptoStream
```
在Dim csCryptoStream As CryptoStream = Nothing

Case Else

在使用此变量之前检查
```
Case/Select
```

警告变量＆csCryptoStream＆＃39;在被赋值之前使用。在运行时可能会导致空引用异常

1 个答案: