试试改成

If rg.RowHeight.toString < 22  Then

Dim Book As New XLS.Book(ProjectPath & "Attachments\\P102月报分部分项工程计价表.xls")
Dim fl As String = ProjectPath & "Reports\\P102月报分部分项工程计价表.xls"
Dim Sheet As XLS.Sheet = Book.Sheets(0) \'引用工作簿的第一个工作表
Book.Build() \'生成细节区
Book.Save(fl) \'保存工作簿

Dim App As New MSExcel.Application
Dim Wb As MSExcel.WorkBook = App.WorkBooks.Open(fl)
Dim Ws As MSExcel.WorkSheet = Wb.WorkSheets(1)
Dim Rg As MSExcel.Range = Ws.UsedRange

For i As Integer = 1 To rg.Rows.count
    Dim c = ws.rows(i)
    c.wrapText = True
    c.EntireRow.AutoFit
    If val(c.RowHeight.toString) < 25  Then
        c.RowHeight = 25
    End If
Next
App.Visible = True