I'm trying to start a form with ShowDialog and it returns DialogResult.Cancel. Why is this?

Question

Progress progress = new Progress();//progress.DialogResult is OK.
if (progress.ShowDialog() != DialogResult.OK)
{//progress.DialogResult is cancel.
    throw new ArgumentException();
}

In the debugger it says that the result is DialogResult.Cancel. Why is this? I have a form with just a progress bar and a label. Nothing more. I have opened and closed some other forms as well if this matters. The form doesn't open.

Progress class:

public partial class Progress : Form
{
    public Progress()
    {
        InitializeComponent();
    }

    bool filesLength = false;

    public void OnWordsChanged()
    {
        if (!filesLength)
        {
            progressBar1.Maximum = Program.numberOfFiles;
            filesLength = true;
        }
        progressBar1.Value = Program.wordsDone;
    }
}

and designer:

 partial class Progress
{
    /// <summary>
    /// Required designer variable.
    /// </summary>
    private System.ComponentModel.IContainer components = null;

    /// <summary>
    /// Clean up any resources being used.
    /// </summary>
    /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
    protected override void Dispose(bool disposing)
    {
        if (disposing && (components != null))
        {
            components.Dispose();
        }
        base.Dispose(disposing);
    }

    #region Windows Form Designer generated code

    /// <summary>
    /// Required method for Designer support - do not modify
    /// the contents of this method with the code editor.
    /// </summary>
    private void InitializeComponent()
    {
        this.label1 = new System.Windows.Forms.Label();
        this.progressBar1 = new System.Windows.Forms.ProgressBar();
        this.SuspendLayout();
        // 
        // label1
        // 
        this.label1.AutoSize = true;
        this.label1.Location = new System.Drawing.Point(13, 13);
        this.label1.Name = "label1";
        this.label1.Size = new System.Drawing.Size(35, 13);
        this.label1.TabIndex = 0;
        this.label1.Text = "label1";
        // 
        // progressBar1
        // 
        this.progressBar1.Location = new System.Drawing.Point(13, 30);
        this.progressBar1.Name = "progressBar1";
        this.progressBar1.Size = new System.Drawing.Size(259, 23);
        this.progressBar1.TabIndex = 1;
        // 
        // Progress
        // 
        this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
        this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
        this.ClientSize = new System.Drawing.Size(284, 261);
        this.Controls.Add(this.progressBar1);
        this.Controls.Add(this.label1);
        this.Name = "Progress";
        this.Text = "Progess";
        this.ResumeLayout(false);
        this.PerformLayout();

    }

    #endregion

    private System.Windows.Forms.Label label1;
    private System.Windows.Forms.ProgressBar progressBar1;
}

Answer 1

This is a normal behavior. You can refer to this answer and from Form.DialogResult Property.

When a form is displayed as a modal dialog box, clicking the Close button (the button with an X in the top-right corner of the form) causes the form to be hidden and the DialogResult property to be set to DialogResult.Cancel. The Close method is not automatically called when the user clicks the Close button of a dialog box or sets the value of the DialogResult property. Instead, the form is hidden and can be shown again without creating a new instance of the dialog box. Because of this behavior, you must call the Dispose method of the form when the form is no longer needed by your application.

Meaning by default, when you close a form it will have DialogResult.Cancel unless it is overridden.