更改其背景色时，将重置文本框的前色，反之亦然（使用PostBack）

Question

I have one main textbox with multiline textmode, and another two textboxes with color textmode, one is to change the text-color and the other one to change the background-color of the main textbox.

The problem is that if I change the background color after changing the text color, the text color will be overridden by black color (I guess this is the default color), or if I change the text color after changing the background color, the background color will be overridden by white color (the default color I guess).

I know the textbox value is posted with PostBack request, but I thought ViewState should store the control information for textbox. It still does not if I enable ViewState for the main textbox explicitly.

Somehow I can fix this problem. But, why does it behave like this?

UPDATE

I have checked this resource: http://www.c-sharpcorner.com/UploadFile/ee01e6/viewstate-for-textbox-in-Asp-Net/

When I use radiobuttons, it works. If I use the textbox as the color-picker, then it does not work.

Is this a bug of textbox when used with TextMode set to Color??

Here is the main textbox:

    <asp:TextBox ID="txt_Editor"
        TextMode="MultiLine"
        Columns="50" Rows="10"
        EnableViewState="true"
        runat="server"></asp:TextBox>

Here are the two:

    <div class="text-muted">Color Options:</div>
    Text-color:
    <asp:TextBox ID="txt_TextColor" 
        AutoPostBack="true" TextMode="Color"
        Text="#000000" runat="server" OnTextChanged="txt_TextColor_TextChanged">
    </asp:TextBox>

    Background-color:
    <asp:TextBox ID="txt_BackColor"
        TextMode="Color" AutoPostBack="true"
        Text="#FFFFFF" runat="server" OnTextChanged="txt_BackColor_TextChanged"></asp:TextBox>

Here is the related part in the CodeBehind file, whenever a color is chosen the colors of the main textbox should be updated accordingly:

    protected void txt_TextColor_TextChanged(object sender, EventArgs e)
    {
        txt_Editor.ForeColor = Color.FromName(txt_TextColor.Text);
    }

    protected void txt_BackColor_TextChanged(object sender, EventArgs e)
    {
        txt_Editor.BackColor = Color.FromName(txt_BackColor.Text);
    }

Answer 1

Got it, the problem has nothing to do with textboxes nor ViewStates, its the Color.FromName, if you use instead ColorTranslator.FromHtml it works perfectly, so I suppose the color returned from Color.FromName is really invalid.

Really an strange bug.

EDIT: Ok, so I checked the resulting colors and it's not really a bug, FromName must be used only on named colors "red", "blue", etc, if you use it this way it creates a color which has these properties (values are examples) "{Name=#6bea55, ARGB=(0, 0, 0, 0)}", as you can see the name has a prepended # and the RGB values are all zeros because it can't parse it, but if you use the translator then it creates a color like this "{Name=ff6bea55, ARGB=(255, 107, 234, 85)}", so what's happening under the hood is that HTML renderer is using the Name property to fill the value of the style property but the ViewState is storing the ARGB values, when you do a postback it restores those ARGB values and thus the color is lost.

Answer 2

您将需要在隐藏字段或视图状态中捕获颜色，并在回发后进行检查。