Cannot convert from string to System.Windows.Forms.Control

Question

I want to set an error message in the variable txtURL but I get the error message Cannot convert from string to System.Windows.Forms.Control.

The error is on this line
frmweb.ErrorMelding.SetError(frmweb.URL, "Je hebt geen url ingegeven");

Here is the code I am using

Webbrowser_Functions.cs

public void Navigeren(frmWeb frmweb)
{
    // Als URL leeg is error melding weergeven
    if (frmweb.pu_txtURL == "")
    {
        frmweb.ErrorMelding.SetError(frmweb.URL, "Je hebt geen url ingegeven");
    }
}

frmWeb.cs

public string pu_txtURL;

public string URL
{
    get { return txtURL.Text; }
    set { txtURL.Text = value; }
}

Logical_Layer.Webbrowser_Functions ww = new Logical_Layer.Webbrowser_Functions();

public void btnNavigeer_Click(object sender, EventArgs e)
{
    txtURL.Text = pu_txtURL;
    ww.Navigeren(this);
}

The error is rather clear. You tried to pass a string to a method that expects a control. Did you mean to write SetError(frmweb.txtUrl,...) perhaps? — Panagiotis Kanavos
– Panagiotis Kanavos, Commented Dec 19, 2017 at 9:57
Crystal ball says that you use the ErrorProvider component to display mistakes. Its first argument requires a Control, not a string. So you'd have to pass txtURL. Which right now is a private variable of the frmWeb class so you can't. The problem is caused by Webbrowser_Functions, it tries to do too much with variables it does not have access to. Consider adding a public method to frmWeb to report the error. Or simply making Navigeren() a method of that form class. — Hans Passant
– Hans Passant, Commented Dec 19, 2017 at 9:58

René Vogt · Accepted Answer · 2017-12-19 10:01:04Z

2

SetError() expects the Control you want to set the error on as first argument, not a string.

So you probably wanted something like:

frmweb.ErrorMelding.SetError(frmweb.txtURL, "Je hebt geen url ingegeven");

But actually it has a smell that the Controls of your frmweb are accessible from outside. It seems better to make Navigeren an instance method of your Form.

edited Dec 19, 2017 at 10:01

answered Dec 19, 2017 at 9:58

René Vogt

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