c# - Object reference not set to an instance of object -

i have function this

public void gettableswithuppercasename() {    sqlconnectionstringbuilder objconnectionstring = new sqlconnectionstringbuilder();    objconnectionstring.datasource = txthost.text;    objconnectionstring.userid = txtusername.text;    objconnectionstring.password = txtpassword.text;    objconnectionstring.initialcatalog = convert.tostring(cmbdatabases.selectedvalue);     sqlconnection sconnection = new sqlconnection(objconnectionstring.connectionstring);     //to open connection.    sconnection.open();     //query select table_names have names in uppercase letters.    string selecttableswithuppercasename = @"select                                                name                                                                                            sysobjects                                                                                             upper(name) collate latin1_general_bin = name collate latin1_general_bin                                                ,                                                   objectproperty(id,n'istable')=1                                               ,                                                   objectproperty(id,n'ismsshipped')=0 ";    //create command object    sqlcommand scommand = new sqlcommand(selecttableswithuppercasename, sconnection);     try    {        //create dataset        dataset dslistoftableswithuppercasename = new dataset("sysobjects");         //create dataadapter object        sqldataadapter sdataadapter = new sqldataadapter(selecttableswithuppercasename, sconnection);         //provides master mapping between sourcr table , system.data.datatable        sdataadapter.tablemappings.add("table", "sysobjects");         //fill dataset        sdataadapter.fill(dslistoftableswithuppercasename);         //bind result combobox foreign key table names        dataviewmanager dvmlistofforeignkeys = dslistoftableswithuppercasename.defaultviewmanager;        dgresultview.datasource = dslistoftableswithuppercasename.tables["sysobjects"];     }     catch(exception ex)     {         //all exceptions handled , written in eventlog.         eventlog log = new eventlog("application");         log.source = "mfdbanalyser";         log.writeentry(ex.message);     }         {        //if connection not closed close connection        if(sconnection.state != connectionstate.closed)        {           sconnection.close();        }     }  } 

and function counting rows generated previous functions. function

null reference exception or object reference not set instance of object..

can me in this... why catching error functions above , working fine other similar functions.

private void updatelabeltext() {     sqlconnectionstringbuilder objconnectionstring = new sqlconnectionstringbuilder();     objconnectionstring.datasource = txthost.text;     objconnectionstring.userid = txtusername.text;     objconnectionstring.password = txtpassword.text;     objconnectionstring.initialcatalog = convert.tostring(cmbdatabases.selectedvalue);      sqlconnection sconnection = new sqlconnection(objconnectionstring.connectionstring);      //to open connection.     sconnection.open();      try     {         int selectedcelltotal = 0;         int counter;          // iterate through selectedcells collection , sum values.         for(counter = 0;counter < (dgresultview.selectedcells.count);counter++)         {             if(dgresultview.selectedcells[counter].formattedvaluetype == type.gettype("system.string"))             {                  string value = null;                   // if cell contains value has not been commited,                  if(dgresultview.iscurrentcelldirty == true)                  {                     value = dgresultview.selectedcells[counter].editedformattedvalue.tostring();                  }                  else                  {                     value = dgresultview.selectedcells[counter].formattedvalue.tostring();                  }                  if(value != null)                  {                     // ignore cells in description column.                     if(dgresultview.selectedcells[counter].columnindex != dgresultview.columns["table_name"].index)                     {                        if(value.length != 0)                        {                           selectedcelltotal += int.parse(value);                        }                     }                  }               }             }              // set labels reflect current state of datagridview.             lbldisplay.text = "there total " + dgresultview.rowcount + cmboperations.selecteditem.tostring();         }         catch(exception ex)         {             //all exceptions handled , written in eventlog.             eventlog log = new eventlog("application");             log.source = "mfdbanalyser";             log.writeentry(ex.message);         }                 {             //if connection not closed close connection             if(sconnection.state != connectionstate.closed)             {                 sconnection.close();             }         }     } 

also lbldisplay.text not taking proper spaces.

waiting reply

ok, don't have answer why you're getting "null reference exception" - few points throw in, nonetheless:

• i use sys.tables instead of sysobjects , having specify type of object query for

• always put disposable sqlconnection , sqlcommand using(.....) { ...... } blocks. way, won't need finally {..} blocks, , .net take care of disposing of objects when they're no longer needed

• why use dataset when have single table inside?? that's unnecessary overhead - use datatable instead!

• don't open sqlconnection - wait 'til last moment, open it, execute query, close again right away

• actually, when using sqldataadapter, don't need open sqlconnection @ - sqldataadapter (and close again after done reading data)

• do not mix retrieval of data database binding ui element - bad practice. gettableswithuppercasename method, should return (like datatable) caller (the ui) , let ui handle binding process

• along same lines: method should not grabbing stuff ui elements (like text boxes) - pass in values method parameters, cleaner code - 1 might able reuse in project day

this how think first method ought like

    public datatable gettableswithuppercasename(string server, string database,                                                  string username, string password)     {         // create datatable         datatable dtlistoftableswithuppercasename = new datatable("tablenames");          sqlconnectionstringbuilder objconnectionstring = new sqlconnectionstringbuilder();         objconnectionstring.datasource = server;;         objconnectionstring.userid = username;         objconnectionstring.password = password;         objconnectionstring.initialcatalog = database;          // define query against sys.tables - easier , cleaner!         string selecttableswithuppercasename =             "select name sys.tables upper(name) collate latin1_general_bin = name collate latin1_general_bin , is_msshipped = 0";          // put sqlconnection , sqlcommand using blocks!         using (sqlconnection sconnection = new sqlconnection(objconnectionstring.connectionstring))         using (sqlcommand scommand = new sqlcommand(selecttableswithuppercasename, sconnection))         {             try             {                 // create dataadapter object                 sqldataadapter sdataadapter = new sqldataadapter(selecttableswithuppercasename, sconnection);                  // fill datatable - no need open connection, sqldataadapter                  // (and close again after done)                 sdataadapter.fill(dtlistoftableswithuppercasename);             }             catch (exception ex)             {                 //all exceptions handled , written in eventlog.                 eventlog log = new eventlog("application");                 log.source = "mfdbanalyser";                 log.writeentry(ex.message);             }         }          // return data table caller         return dtlistoftableswithuppercasename;     }