Changing the color of a text box depending on its content

Question

I have in a VS2005 C++ Form application a table adapter and a Text box that displays data from a specific column. What I want to do is to have its color changed on whether the content is >0 or <0. I tried adding this:

if(this->CSumTextBox->TabIndex<0) 
{
    this->CSumTextBox->ForeColor = System::Drawing::Color::Red;
}

But it doesn't work... (I didn't really believe TabIndex was the correct function, but it seemed the only one close) Help please

Edit: CSum is a double. Here is the whole code for CsumTextBox:

// 
// CSumTextBox
// 
this->CSumTextBox->Anchor = static_cast<System::Windows::Forms::AnchorStyles>((System::Windows::Forms::AnchorStyles::Bottom | System::Windows::Forms::AnchorStyles::Left));
this->CSumTextBox->BackColor = System::Drawing::SystemColors::Window;
this->CSumTextBox->DataBindings->Add((gcnew System::Windows::Forms::Binding(L"Text", this->sumclosedpnlBindingSource, L"CSum", true)));
this->CSumTextBox->Location = System::Drawing::Point(214, 632);
this->CSumTextBox->Name = L"CSumTextBox";
this->CSumTextBox->Size = System::Drawing::Size(86, 20);
this->CSumTextBox->TabIndex = 7;

It is in the Form Header (the whole program is a GUI, so almost everything is in there...)

Edit: Maybe if I check the data binding source's Value it would work, but how can I do that? (Does a this->sumclosedpnlBindingSource->returnvalue(CSum) or something like that exist?)

Answer 1

What do you mean by this:

… have its color changed on whether the content is >) …

To get access to the content of the text box, use its Text property. To test for a numeric value, you need to convert it to an integer (or other number type) first:

int value = System::Int32::Parse(CSumTextBox->Text);

if (value < 0)
    CSumTextBox->ForeColor = System::Drawing::Color::Red;

Answer 2

int val = -1;
if(!Int32::TryParse(CSumTextBox->Text) || val != 0)
{
   CSumTextBox->ForeColor = System::Drawing::Color::Red;
}

This will check that the value in the textbox actually converts to an integer, and that the value is not 0.