程序代码：

Public Class Form1
    Sub maxlength(ByVal s$, ByRef max$)
        Dim n$, i%
        s = LTrim(s)
        i = InStr(s, " ")

        Do While i <> 0

            n = Mid(s, 1, i - 1)
            If Len(n) < Len(max) Then max = n
            s = Mid(s, i + 1)
            i = InStr(s, " ")

        Loop
        If Len(s) > Len(max) Then max = s
    End Sub
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim s, m As String
        s = TextBox1.Text

        Call maxlength(s, m)
        TextBox2.Text = m
    End Sub
End Class

程序代码：

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
   
    Dim arr As String() = TextBox1.Text.Split(" ")
    Dim str As String = ""
    For i = 0 To arr.Count - 1
        If arr(i).Length > str.Length Then str = arr(i)
    Next
    TextBox2.Text = str

End Sub

程序代码：

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
  
    For Each str As String In TextBox1.Text.Split(" ")
        If str.Length > TextBox2.Text.Length Then TextBox2.Text = str
    Next

End Sub