Wie kann ich ermitteln, ob eine Sharepoint-Listenelement vorhanden ist, basierend auf ein paar bekannte Werte?

CRUD-Beispiel, die Verwendung von REST

wie gewünscht mit SharePoint 2010

Die Schönheit eines RESTful service --> alles geschieht über HTTP

So können Sie mit reinem JavaScript über XMLHttpRequest

oder JQuery über $.ajax

oder MicrosoftAjax.js über Sys.Net.WebRequest

wie dieses Beispiel zeigt, da es bereits in einer SharePoint 2010-Webpart

//test rest on SharePoint 2010
testREST();

function testREST() {
  /*
  **  List name: Test List (collapse spaces)
  **  Find list item - Set query in url --> ListName?$filter=
  **  Or access by list item id --> ListName(id)
  */
  invokeRequest({
    //make GET request with url query
    //REST also allows expansion of lookup fields
    // --  here, i check `ModifiedBy` for `[Me]`
    'url': "TestList?$filter=" +
           "TextColumn eq 'row 1' and " +
           "NumberColumn lt 3 and " +
           "ModifiedById eq " + _spPageContextInfo.userId,

    //GET request
    'verb': "GET",

    //not needed for GET requests
    'body': null,
    'match': null,
    'method': null,

    //on complete
    'success': function (jsonObj) {
      //check the results of our query, returned in array: jsonObj.d.results
      //fyi -- if id used -- ListName(id) -- no array, one object: jsonObj.d
      if (jsonObj.d.results.length === 0) {
        //nothing found, insert new item
        insertItem();
      } else {
        //check field for _first_ item returned -- NumberColumn
        if (jsonObj.d.results[0].NumberColumn < 2) {
          //update if less than 2
          updateItem(jsonObj.d.results[0]);
        } else {
          //delete if greater than or equal to 2
          deleteItem(jsonObj.d.results[0]);
        }
      }
    },
    'fail': function (errCode, errMessage) {
      console.log(errCode + ' = ' + errMessage);
    },
  });
}

function insertItem() {
  /*
  **  List name: Test List
  **  Insert list item
  */
  invokeRequest({
    //make POST request for insert
    'url': "TestList",
    'verb': "POST",

    //use MicrosoftAjax.js to serialize our new list item
    'body': Sys.Serialization.JavaScriptSerializer.serialize({
      //set a key: value according to the column names in the list
      Title: "TEST",
      TextColumn: "row 1",
      EmployeeId: _spPageContextInfo.userId,
      NumberColumn: 1,
      DateColumn: new Date()
    }),

    //new item -- match & method not needed
    'match': null,
    'method': null,

    //on complete
    'success': function (jsonObj) {
      //print new list item to console
      var s = '';
      for (var key in jsonObj.d) {
        if (jsonObj.d.hasOwnProperty(key)) {
          s += key + ' = ' + jsonObj.d[key] + '\n';
        }
      }
      console.log('new list item\n' + s);
    },
    'fail': function (errCode, errMessage) {
      console.log(errCode + ' = ' + errMessage);
    },
  });
}

function updateItem(listItem) {
  /*
  **  List name: Test List
  **  Update list item
  */
  invokeRequest({
    //make POST request for insert -- set ID on url
    'url': "TestList(" + listItem.Id + ")",
    'verb': "POST",

    //serialize our updates -- literal w/field name keys
    'body': Sys.Serialization.JavaScriptSerializer.serialize({
      Title: listItem.TextColumn + " test",
      NumberColumn: Number(listItem.NumberColumn) + 1
    }),

    //send the -- etag match -- for our update
    'match': listItem.__metadata.etag,

    //MERGE allows updates to one or more fields
    'method': "MERGE",

    //on complete
    'success': function (jsonObj) {
      //print request body -- _updated fields_ -- to console
      var newFields = Sys.Serialization.JavaScriptSerializer.deserialize(jsonObj.body);
      var s = '';
      for (var key in newFields) {
        if (newFields.hasOwnProperty(key)) {
          s += key + ' = ' + newFields[key] + '\n';
        }
      }
      console.log('updated list item\n' + s);
    },
    'fail': function (errCode, errMessage) {
      console.log(errCode + ' = ' + errMessage);
    },
  });
}

function deleteItem(listItem) {
  /*
  **  List name: Test List
  **  Delete list item
  */
  invokeRequest({
    //make POST request for delete -- set ID on url
    'url': "TestList(" + listItem.Id + ")",
    'verb': "POST",

    //no body needed for delete
    'body': null,

    //send the match for delete method
    'match': listItem.__metadata.etag,
    'method': "DELETE",

    //on complete
    'success': function (jsonObj) {
      //print request url for delete request
      console.log('deleted list item request\n' + jsonObj.url);
    },
    'fail': function (errCode, errMessage) {
      console.log(errCode + ' = ' + errMessage);
    },
  });
}

//invoke web request using [MicrosoftAjax.js](https://msdn.microsoft.com/en-us/library/vstudio/bb397536(v=vs.100).aspx)
function invokeRequest(requestObj) {
  //new web request
  var webRequest = new Sys.Net.WebRequest();

  //set request headers
  webRequest.get_headers()['Cache-Control'] = 'no-cache';
  webRequest.get_headers()['Accept'] = 'application/json';
  webRequest.get_headers()['Content-Type'] = 'application/json';

  //set etag match
  if (requestObj.match !== null) {
    webRequest.get_headers()['If-Match'] = requestObj.match;
  }

  //set method
  if (requestObj.method !== null) {
    webRequest.get_headers()['X-HTTP-Method'] = requestObj.method;
  }

  //set request verb
  webRequest.set_httpVerb(requestObj.verb);

  //set request body
  if (requestObj.body !== null) {
    webRequest.set_body(requestObj.body);
  }

  //set request url
  webRequest.set_url(
    _spPageContextInfo.webServerRelativeUrl + '/_vti_bin/ListData.svc/' + requestObj.url
  );

  //set user context
  webRequest.set_userContext(requestObj);

  //set completed callback and invoke request
  webRequest.add_completed(serviceComplete);
  webRequest.invoke();
}

//process web request
function serviceComplete(executor, args) {
  //check response
  if (executor.get_responseAvailable()) {
    //check status
    switch (executor.get_statusCode()) {
      case 200:   //OK
      case 201:   //Created
        //raise success callback - pass list item
        executor.get_webRequest().get_userContext().success(
          executor.get_object()
        );
        break;

      case 202:   //Accepted
      case 203:   //Non auth info
      case 204:   //No content
      case 205:   //Reset
      case 206:   //Partial
      case 1223:  //No content (SP)
        //raise success callback - pass original request object
        executor.get_webRequest().get_userContext().success(
          executor.get_webRequest().get_userContext()
        );
        break;

      //Error
      default:
        //raise fail callback - pass status
        executor.get_webRequest().get_userContext().fail(
          executor.get_statusCode(),
          executor.get_statusText()
        );
    }
  } else {
    //check timeout
    if (executor.get_timedOut()) {
      executor.get_webRequest().get_userContext().fail(408,'Request Timeout');
    } else {
      //check abort
      if (executor.get_aborted()) {
        executor.get_webRequest().get_userContext().fail(800,'Request Aborted');
      } else {
        executor.get_webRequest().get_userContext().fail(801,'Unknown Error');
      }
    }
  }
}

mehr auf Namenskonventionen in SharePoint 2010

mehr auf spPageContextInfo