How do I solve this exception

Question

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Hi,

I am using the following the following code for saving path of folder browse into settings

C#

private void btnDatabaseGwMsgsBrowse_Click(object sender, EventArgs e)
        {
            Properties.Settings.Default.GatewayDataPath = AttachFiles(txtDatabaseGwMsgsFile);
            
        }

        private string AttachFiles(Control control)
        {
            OpenFiles.Filter = Constants.FILTER_GW_DATABASE;
            OpenFiles.Title = Constants.FILTER_GW_DATABASE;

            DialogResult result = this.OpenFiles.ShowDialog();

            if (result == DialogResult.OK)
            {
                control.Text = string.Empty;
                control.Text = OpenFiles.SafeFileName.Trim();
            }
            return (OpenFiles.FileName.Replace(OpenFiles.SafeFileName, " ").Trim());
            //if (result == DialogResult.OK)
            //    DgView.Rows[e.RowIndex].Cells[e.ColumnIndex - 1].Value = OpenFiles.SafeFileName.Trim();
        }

I have given like below in designer

C#

private System.Windows.Forms.OpenFileDialog OpenFiles;

warning:
Field 'SCANLA.GatewayMsgIDs.OpenFiles' is never assigned to, and will always have its default value null

when I am trying to run the program

Exception:

C#

An unhandled exception of type 'System.NullReferenceException' occurred

Posted 7-Feb-14 2:13am

Member 10408451

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EduChapow 7-Feb-14 8:15am

which row this exception is throwing?

2 solutions

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Fredrik Bornander · Answer 1 · 2014-02-07T02:19:00

The error messages are telling you all you need to know;

Field 'SCANLA.GatewayMsgIDs.OpenFiles' is never assigned to, and will always have its default value null

Means that you're never assigning the variable OpenFiles, so it will always be null and you will get a NullReferenceException thrown at you as soon as you try to use one of its members.

Make sure you assign the OpenFiles variable before first use and you'll be fine.

Hope this helps,
Fredrik

Pascal-78 · Answer 2 · 2014-02-07T02:21:00

Solution 2

The warning is the key.

the OpenFiles object is never assign, and when you use it, you get the NullReferenceException.

C#

private System.Windows.Forms.OpenFileDialog OpenFiles = new System.Windows.Forms.OpenFileDialog();

should correct your problem.

Posted 7-Feb-14 2:21am

Pascal-78

Comments

Member 10408451 7-Feb-14 13:14pm

Hi,
I tried like below but the open file dialog box is opening again and again when I press ok

private System.Windows.Forms.OpenFileDialog OpenFiles = new System.Windows.Forms.OpenFileDialog();

Pascal-78 7-Feb-14 14:53pm

The OpenFileDialog window is displayed only when OpenFiles.ShowDialog() is called. If you do not have this line elsewhere in your code, that means your AttachFiles method is called.
You should debug your code, put a breakpoint on the ShowDialog line and then look at the call-stack to understand why it's repeating this.