exception - MVC5 / C# - Cannot perform runtime binding on a null reference -


i'm trying figure out what's causing cannot perform runtime binding on null reference error code:

var query = "select id, username, list_order, loggedin " +              "from aspnetusers" +             "where loggedin = 1" +              "order list_order asc";  var conn = new sqlconnection(system.configuration.configurationmanager.connectionstrings["defaultconnection"].connectionstring); var cmd = new sqlcommand(query, conn);    conn.open(); var rdr = cmd.executereader(); var n = 0; while(rdr.read()) {     if (convert.tostring(rdr["username"]) != null)     {         viewbag.speakers[n] = new string[4] {             convert.tostring(rdr["id"]),             convert.tostring(rdr["username"]),             convert.tostring(rdr["list_order"]),             convert.tostring(rdr["loggedin"])          };          //exception details: microsoft.csharp.runtimebinder.runtimebinderexception: cannot          //perform runtime binding on null reference         n++;     } }

the n++ increment seems cause of error , don't understand why.

updated code reflect possible solutions. however, error still remains.

tried same result:

if (!string.isnullorwhitespace(convert.tostring(rdr["username"]))) {         list<string> speakers = new list<string>();         speakers.add(convert.tostring(rdr["id"]));         speakers.add(convert.tostring(rdr["username"]));         speakers.add(convert.tostring(rdr["list_order"]));         speakers.add(convert.tostring(rdr["loggedin"]));          viewbag.speakers[n] = speakers;         n++; }

there 2 issues in code:

consider this:

public actionresult index() {    int n = 0;    viewbag.speakers[n] = 5;    return view(); }

this simplified piece of code throws cannot perform runtime binding on null reference since speakers not defined (null reference).

you can fix defining speakers in dynamic viewbag before loop:

viewbag.speakers = new list<string>();

the second issue:

viewbag.speakers[n] = speakers;

speakers in code list, might want define viewbag.speakers list<list<string>> , call .add(speakers) instead of accessing using index (you might index out of range)


Comments

Post a Comment

Popular posts from this blog

asynchronous - C# WinSCP .NET assembly: How to upload multiple files asynchronously -

i using winscp .net assembly uploading files. want upload multiple files asynchronous way. have created method works single upload. public class uploadingdata { private sessionoptions _sessionoptions; private session _session; //connection etc private void onconnected() { foreach (var fileinfo in localfileslist) { var task = task.factory.startnew(() => uploadfilesasync(fileinfo)); } } private async task uploadfilesasync(string file) { string remotefilepath = _session.translatelocalpathtoremote(file, @"/", "/test_data_upload"); var uploading = _session.putfiles(file, remotefilepath, false); //when done await task.run(() => thread.sleep(1000)); } } please suggest me correct way. thanks you can use backgroundworker class this: string[] images = new string[50]; foreach (var path in images) { backgroundworker
Read more

aws api gateway - SerializationException in posting new Records via Dynamodb Proxy Service in API -

i getting "__type": "com.amazon.coral.service#serializationexception" as reply in postman & in test console in api gateway trying post record directly dynamodb using api proxy services.. referring aws article - https://aws.amazon.com/blogs/compute/using-amazon-api-gateway-as-a-proxy-for-dynamodb/ here's mapping { "tablename": "tablenamegoeshere", "item": { "id" : "$context.requestid" "eventname" : "$input.path('$.eventname')", "timestamp" : $input.path('$.timestamp'), "answers": "$util.parsejson($input.path('$.answers'))" } } update: did asked ... , worked if try add array of json objects gives me above same error - here's trying now. please - couldnt find on google well #set($inputroot = $input.path('$')) { "tablename": "answer", "item": {
Read more

asp.net - Problems sending emails from forum -

i have been redesigning site has message board, has been written guy looked after site. it has few problems , written in .asp , uses .mdb files database. you can see whole thing here . feel free post if helps, test thing have set using original files , new database. the basic problem when posts message, supposed email sent them, have posted it. when replies, originator supposed message, replier has been posted. i’d have thought @ point in process there should script/file in postmessage.asp? the postmessage.asp page below. <% option explicit %> <!-- #include virtual="common/adovbs.inc" --> <html> <head> <meta http-equiv="content-type" content="text/html; charset=windows-1252"> <meta name="generator" content="microsoft frontpage 4.0"> <meta name="progid" content="frontpage.editor.document"> <title>new page 2</title> <base target="_self"
Read more