Question

As the title says, I have a method that throws a NullReferenceException in my DataGridView Binding method.

Here is my code (simplified):

private void GridViewBinding(string sortExpression, string direction)
        { 

             string lang = string.Empty;
             Regex appnoRegex = new Regex("\\d{4}(-)\\d{4}(-)\\d{1}");
             int colCount = gvData.Columns.Count;

            DataView dv = GetData();
            //DataView dvApplication = GetApplicationsData();

            //Sorting only on postback, else rel. docs won't appear
            if (Page.IsPostBack)
            {
                dv.Sort = sortExpression + " " + direction;
            }

            lblTotal.Text = dv.Count.ToString();

            gvData.DataSource = dv;
            gvData.DataKeyNames = new string[] { "InterventionID", "ItemNumber" };
            gvData.DataBind();

            ChangeHeaders(_docTypeQueryStr, colCount, appnoRegex);
}

The change header Method:

private void ChangeHeaders(string DocType, int colCount, Regex appnoRegex)
        {
            switch (DocType.ToUpper())
            {
                //intervention documents
                case "I":
                    lblDocumentTypeTitle.Text = Resources.GeneralResouces.lblTypeTitleInterventionsText;
                    lblIntervenorLastName.Text = Resources.GeneralResouces.lblIntervenorLastNameInterventionText;
                    break;
                //Replies document
                case "R":
                    lblDocumentTypeTitle.Text = Resources.GeneralResouces.lblTypeTitleRepliesText;
                    lblIntervenorLastName.Text = Resources.GeneralResouces.lblIntervenorLastNameRepliesText;
                    break;
                //Answer Documents
                case "AR":
                    lblDocumentTypeTitle.Text = Resources.GeneralResouces.lblTypeTitleAnswersText;
                    lblIntervenorLastName.Text = Resources.GeneralResouces.lblIntervenorLastNameAnswerText;
                    break;
                //if none of teh above
                default:
                    //Notice of consultations
                    if (applicationCount == 0 && !appnoRegex.IsMatch(_eventNoQueryStr))
                    {
                        lblIntervenorLastName.Text = Resources.GeneralResouces.lblIntervenorText;
                    }
                    //Part 1 applications
                    else
                    {
                        //Part 1 applications and notices with applications
                        if (applicationCount != 0 || appnoRegex.IsMatch(_eventNoQueryStr))
                        {
                            lblIntervenorLastName.Text = Resources.GeneralResouces.lblIntervenorWithApplicationsText;
                        }
                    }
                    break;
            }

This is the stack trace I get:

[NullReferenceException: Object reference not set to an instance of an object.]
   Interventions._Default.ChangeHeaders(String DocType, Int32 colCount, Regex appnoRegex) +13
   Interventions._Default.GridViewBinding(String sortExpression, String direction) +331
   Interventions._Default.Page_Load(Object sender, EventArgs e) +888
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35
   System.Web.UI.Control.OnLoad(EventArgs e) +91
   System.Web.UI.Control.LoadRecursive() +74
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2207

From what I understood of it, the error comes from theChangeHeaders method. I tried putting the ChangeHeaders method in comments and there were no more errors. That told me the error was really from the ChangeHeaders method. However, it is the first time that I get a NUllReferenceException from a Method and I am lost as to why it is doing that. Specially that the said method is in the code and there are no typo when I call it.

How can I fix this, thanks.

Answer 1

Check the value of _docTypeQueryStr.

Probably you are passing a null value to ChangeHeaders and doing a ToUpper().