主题：[求助] &= 在代码中是什么意思

Dim str As String = ""
For Each c As Col In CurrentTable.Cols
    str &= c.Name & "(" & c.Caption & ")|"
Next
e.Form.Controls("CheckedListBox1").ComboList = str.Trim("|")

Dim clist As WinForm.CheckedListBox = e.Form.Controls("CheckedListBox1")
For Each c As Col In CurrentTable.Cols
    clist.SetItemChecked(c.Index, not c.Visible)
Next

像这种写法（&= ）是什么意思？帮助里面也没有搜到  印象中还有一些类似的，谢谢