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Object reference not set to an instance of an object. RRS feed

  • Question

  • User1519602350 posted

    I am unable to get the below error. Please help.

    Object reference not set to an instance of an object.

    Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

    Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

    Source Error:

    Line 58:                   <legend>All Widgets In Layer</legend>
    Line 59:             foreach (var group in widgets) {
    Line 60: <h4>@zones.FirstOrDefault(z => z.Id == group.Key).Name (Zone @group.Key)</h4> Line 61:                 foreach (var widget in group) {
    Line 62:                     if (widget.WidgetName != null) {

    Wednesday, June 26, 2013 9:57 AM

Answers

  • User-610330605 posted

    It means you are trying to access some property of an instance of an object which is null.

    Check if @zones or anything else in that line of code is null.

    • Marked as answer by Anonymous Thursday, October 7, 2021 12:00 AM
    Wednesday, June 26, 2013 10:08 AM
  • User281315223 posted

    Based on the message that you are receiving, it is likely that there aren't any zones that meet your specific constraint (with an Id property set to the key of the group).

    If that is the case then your FirstOrDefault() method will return a null value and then when you attempt to reference the Name property of your null object (which wasn't found), you'll receieve this null reference exception.

    You may consider adding the appropriate logic in there to check if an item exists within your collection (this can be done using the .Any() method) and if it does contain a value then reference it accordingly : 

    @if(zones.Any(z => z.Id == group.Key)){
        <h4>@zones.FirstOrDefault(z => z.Id == group.Key).Name(Zone @group.Key)</h4>
    }



    • Marked as answer by Anonymous Thursday, October 7, 2021 12:00 AM
    Wednesday, June 26, 2013 10:17 AM

All replies

  • User-610330605 posted

    It means you are trying to access some property of an instance of an object which is null.

    Check if @zones or anything else in that line of code is null.

    • Marked as answer by Anonymous Thursday, October 7, 2021 12:00 AM
    Wednesday, June 26, 2013 10:08 AM
  • User-1980594115 posted

    One of your variables / objects contains a null value.   Test to make sure that group.Key and the other objects are not null.   If you are using Visual Studio, you can place a break point on line 60 and mouse over each var and find out what's null, then you can figure out why.

     

    Wednesday, June 26, 2013 10:13 AM
  • User281315223 posted

    Based on the message that you are receiving, it is likely that there aren't any zones that meet your specific constraint (with an Id property set to the key of the group).

    If that is the case then your FirstOrDefault() method will return a null value and then when you attempt to reference the Name property of your null object (which wasn't found), you'll receieve this null reference exception.

    You may consider adding the appropriate logic in there to check if an item exists within your collection (this can be done using the .Any() method) and if it does contain a value then reference it accordingly : 

    @if(zones.Any(z => z.Id == group.Key)){
        <h4>@zones.FirstOrDefault(z => z.Id == group.Key).Name(Zone @group.Key)</h4>
    }



    • Marked as answer by Anonymous Thursday, October 7, 2021 12:00 AM
    Wednesday, June 26, 2013 10:17 AM