This expression was expected to have type string
<p>I am trying to merge values from 5 textboxes in to a string to display in a label. However I am getting this error message</p>

<pre><code>This expression was expected to have type string but here has type string -&gt; string -&gt; string -&gt; string -&gt; string
</code></pre>

<p>I can show the anyone textbox value into the label. 
Here is the code I as using:</p>

<pre><code>let temp = self.Factory.Backing(&lt;@ self.Temp @&gt;, "")
let ph = self.Factory.Backing(&lt;@ self.PH @&gt;, "")
let soil = self.Factory.Backing(&lt;@ self.SOIL @&gt;, "")
let slope = self.Factory.Backing(&lt;@ self.SLOPE @&gt;, "")
let aspect = self.Factory.Backing(&lt;@ self.ASPECT @&gt;, "")

let display = self.Factory.Backing(&lt;@ self.Display @&gt;, "")

let goCommand = self.Factory.CommandSyncParam(fun param -&gt; self.Display &lt;- 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 &lt;- value
member x.PH with get() = ph.Value and set value = ph.Value &lt;- value
member x.SOIL with get() = soil.Value and set value = soil.Value &lt;- value
member x.SLOPE with get() = slope.Value and set value = slope.Value &lt;- value
member x.ASPECT with get() = aspect.Value and set value = aspect.Value &lt;-value
member x.Display with get() = display.Value and set value = display.Value &lt;- value
member x.GoCommand = goCommand  
</code></pre>

<p>I found this code <a href="https://stackoverflow.com/questions/1779048/how-do-i-concatenate-a-list-of-strings-in-f">How do I concatenate a list of strings in F#?</a> and  this is what output that I want. So I tried the this code with with my values.</p>

<pre><code>let strings =["temp.Value"; "ph.Value"; "soil.Value"]

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

printfn "%s"
</code></pre>

<p>I got this as the output:</p>

<pre><code>temp.Value
ph.Value
soil.Value
</code></pre>

<p>So how do you get the Value of each category to show up and how to merge it to the "let goCommand?"</p>

<p>edited per request to showing the xaml code</p>

<pre><code>        &lt;TextBox Grid.Row="3" Grid.Column="1" FontSize="14" Text="{Binding TEMP}"/&gt;
    &lt;TextBox Grid.Row="4" Grid.Column="1" FontSize="14" Text="{Binding PH}"/&gt;
    &lt;TextBox Grid.Row="5" Grid.Column="1" FontSize="14" Text="{Binding SOIL}"/&gt;
    &lt;TextBox Grid.Row="6" Grid.Column="1" FontSize="14" Text="{Binding SLOPE}"/&gt;
    &lt;TextBox Grid.Row="7" Grid.Column="1" FontSize="14" Text="{Binding ASPECT}" Grid.ColumnSpan="3" Margin="0,0,16,0" /&gt;
    &lt;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}"/&gt;
</code></pre>