Converting VB.NET to Visual Cobol

I'm converting this VB.NET code to Visual Cobol but I'm
with difficulty in the declaration: declare a() as binary-char unsigned occurs any = type Encoding::UTF8::GetBytes(SourceText)

VB.NET code running

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim SourceText As String = "1234567890"
    Dim a() As Byte
    a = Encoding.UTF8.GetBytes(SourceText)
    Dim b As Byte()
    Dim c As New SHA512Managed
    b = c.ComputeHash(a)
    Dim d As String = Convert.ToBase64String(b)
End Sub

Visual Cobol code with error.

 method-id button1_Click final private.
 procedure division using by value sender as object e as type System.EventArgs.
     declare sourceText as string = "1234567890"
     declare a() as binary-char unsigned occurs any = type Encoding::UTF8::GetBytes(SourceText)
     declare b as binary-char unsigned occurs any
     declare c as type SHA512Managed
     set b to c::ComputeHash(a)           
     declare d as string = type Convert::ToBase64String(b)         
     set tbxOut::Text to d       
 end method.

Any suggestion?