此表达式应具有字符串类型

Question

我正在尝试将 5 个文本框的值合并到一个字符串中以显示在标签中。但是我收到此错误消息

This expression was expected to have type string but here has type string -> string -> string -> string -> string

我可以在标签中显示任何人的文本框值。这是我使用的代码：

let temp = self.Factory.Backing(<@ self.Temp @>, "")
let ph = self.Factory.Backing(<@ self.PH @>, "")
let soil = self.Factory.Backing(<@ self.SOIL @>, "")
let slope = self.Factory.Backing(<@ self.SLOPE @>, "")
let aspect = self.Factory.Backing(<@ self.ASPECT @>, "")

let display = self.Factory.Backing(<@ self.Display @>, "")

let goCommand = self.Factory.CommandSyncParam(fun param -> self.Display <- sprintf "The data that has been enter is:\n%s,\n %s,\n %s,\n %s,\n %s" param)

member x.TEMP with get() = temp.Value and set value = temp.Value <- value
member x.PH with get() = ph.Value and set value = ph.Value <- value
member x.SOIL with get() = soil.Value and set value = soil.Value <- value
member x.SLOPE with get() = slope.Value and set value = slope.Value <- value
member x.ASPECT with get() = aspect.Value and set value = aspect.Value <-value
member x.Display with get() = display.Value and set value = display.Value <- value
member x.GoCommand = goCommand

我找到了这段代码 How do I concatenate a list of strings in F#?，这就是我想要的输出。所以我用我的价值观尝试了这段代码。

let strings =["temp.Value"; "ph.Value"; "soil.Value"]

let r = strings |> List.fold (fun r s -> r + s + "\n") ""

printfn "%s"

我得到这个作为输出：

temp.Value
ph.Value
soil.Value

那么如何让每个类别的值显示出来以及如何将其合并到 "let goCommand?"

根据请求进行编辑以显示 xaml 代码

        <TextBox Grid.Row="3" Grid.Column="1" FontSize="14" Text="{Binding TEMP}"/>
    <TextBox Grid.Row="4" Grid.Column="1" FontSize="14" Text="{Binding PH}"/>
    <TextBox Grid.Row="5" Grid.Column="1" FontSize="14" Text="{Binding SOIL}"/>
    <TextBox Grid.Row="6" Grid.Column="1" FontSize="14" Text="{Binding SLOPE}"/>
    <TextBox Grid.Row="7" Grid.Column="1" FontSize="14" Text="{Binding ASPECT}" Grid.ColumnSpan="3" Margin="0,0,16,0" />
    <Button Margin="0,31,0,652" Grid.Row="8" FontSize="16" Content="Submit" Foreground="DarkBlue" FontWeight="Heavy" Background="LightBlue"
        Command="{Binding GoCommand}" CommandParameter="{Binding TEMP, PH, SOIL,SLOPE, ASPECT}"/>

Answer 1

您的属性 (x.TEMP,...) 可从 MainViewModel 获得 - 您无需尝试将它们的值作为参数传输。所以需要使用不带任何参数的命令：

.xaml:

    <Button Margin="0,31,0,652" Grid.Row="8" FontSize="16"
     Content="Submit" Foreground="DarkBlue" FontWeight="Heavy" 
Background="LightBlue" Command="{Binding GoCommand}" />

.fs:

let display = self.Factory.Backing(<@ self.Display @>, "")

let go() = 
    self.Display <- sprintf "The data that has been enter is:\n%s,\n %s,\n %s,\n %s,\n %s" 
        self.TEMP self.PH self.SOIL self.SLOPE self.ASPECT

let goCommand = self.Factory.CommandSync(go)

编辑：

完整.fs:

type MainViewModel() as self = 
    inherit ViewModelBase()    

    let temp = self.Factory.Backing(<@ self.TEMP @>, "")
    let ph = self.Factory.Backing(<@ self.PH @>, "")
    let soil = self.Factory.Backing(<@ self.SOIL @>, "")
    let slope = self.Factory.Backing(<@ self.SLOPE @>, "")
    let aspect = self.Factory.Backing(<@ self.ASPECT @>, "")

    let display = self.Factory.Backing(<@ self.Display @>, "")

    let go() = 
        self.Display <- sprintf "The data that has been enter is:\n%s,\n %s,\n %s,\n %s,\n %s" 
            self.TEMP self.PH self.SOIL self.SLOPE self.ASPECT

    let goCommand = self.Factory.CommandSync(go)

    member x.TEMP with get() = temp.Value and set value = temp.Value <- value
    member x.PH with get() = ph.Value and set value = ph.Value <- value
    member x.SOIL with get() = soil.Value and set value = soil.Value <- value
    member x.SLOPE with get() = slope.Value and set value = slope.Value <- value
    member x.ASPECT with get() = aspect.Value and set value = aspect.Value <-value
    member x.Display with get() = display.Value and set value = display.Value <- value
    member x.GoCommand = goCommand

此表达式应具有字符串类型

This expression was expected to have type string

data-binding

wpf

xaml

f#

string-concatenation