CODEWITHSUNDEEP
c#winforms
T.J.
T.J.

Reputation: 57

How do test if a textbox is null using a list of textbox controls?

I have created a list of the all the textboxes on a tab control in my winforms, c# application. Now what I would like to do is check each textbox in the list and test to see if that textbox is empty. If it is I would like to use the error provider to let the user know it needs to be filled. Here is the code I am using now.

//gathers the controls and adds them to a list on the main form
public static List<Control> GetControls(Control form, string type)
    {
        var controlList = new List<Control>();
        foreach (Control childControl in form.Controls)
        {
            if (childControl.Name.Contains(type))
            {
                controlList.Add(childControl);
            }
            if (childControl.HasChildren) GetControls(form, type);
        }
        return controlList;
    }


//Created in a class called DataVerification
public bool IsNotEmpty(string value, out string errorMessage)
    {
        errorMessage = "";
        if (value.Length == 0)
        {
            errorMessage = "This Field Is Required";
            return false;
        }
        return false;
    }


//method that uses the DataVerification class and the error provider
 public void IsNotEmpty()
    {
        availableControls = GetControls(this.tabPage1, "Text");
        string errorMessage;
        DataVerification verify = new DataVerification();
        foreach (Control c in availableControls)
        {
            if (!verify.IsNotEmpty(c.Text, out errorMessage))
            {
                ErrorProvider.SetError(c, errorMessage);
            }
        }
    }

Even if I could just display a messagebox that lets the user know which textboxes are empty would be fine. Any help would be appreciated. Thanks in advance.

Upvotes: 0

Views: 1251

Answers (4)

ahmad
ahmad

Reputation: 11

The method IsNotEmpty is a boolean one; always return false.

public bool IsNotEmpty(string value, out string errorMessage)
{
    errorMessage = "";
    if (value.Length == 0)
    {
        errorMessage = "This Field Is Required";
        return true; //instead of false
    }
    return false;
}

Upvotes: 1

OmarOthman
OmarOthman

Reputation: 1728

I'm not sure I understand the question, but if you want to know where the TextBox controls are and verify only these, you can do the following:

foreach (Control c in availableControls)
{
    TextBox t = c as TextBox;
    if (t != null && !verify.IsNotEmpty(t.Text, out errorMessage))
        ErrorProvider.SetError(t, errorMessage);
}

Upvotes: 0

MunkiPhD
MunkiPhD

Reputation: 3644

I don't exactly understand what your question is...

What you can use to test if a textbox's value is empty is the String.IsNullOrEmpty();

Instead of: 

 if (!verify.IsNotEmpty(c.Text, out errorMessage))
            {
                ErrorProvider.SetError(c, errorMessage);
            }

Just do this:

 if (String.IsNullOrEmpty(c.Text))
            {
                ErrorProvider.SetError(c, "This field is required!");
            }

Also, I recommend you change your naming scheme a tad. It's good practice to have methods and such be in the 'truthful' form. So instead of IsNotEmpty, IsEmpty would be easier to read/maintainable. That line of !verify.IsNotEmpty() throws a double negative!

EDIT: As ahmad said: your method always returns false. It should read:

public bool IsNotEmpty(string value, out string errorMessage)
    {
        if (value.Length == 0)
        {
            errorMessage = "This Field Is Required";
            return false;
        }
        return true;
    }

Upvotes: 0

Prahlad Yeri
Prahlad Yeri

Reputation: 3653

You can cast the control to a text-box in this manner:

            TextBox t = (TextBox)c;

and then use the t.Text to perform validation.

Upvotes: 0

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