SharePoint CSOM 查询返回每个字段 null

Question

I want to retrive some fields with CAML Query - everytime when i execute query for example:

                query.ViewXml = string.Format(@"
                <View>
                    <Query>
                        <Where>
                        <Eq>
                            <FieldRef Name='IDCardNumber' LookupId='TRUE'/>
                            <Value Type='Text'>12345</Value>
                        </Eq>
                        </Where>
                    </Query>
                    </View>
                    < ViewFields >
                       < FieldRef Name = 'Title' />
                    </ ViewFields >)");

                var items = list.GetItems(query);
                clientContext.Load(items);
                clientContext.ExecuteQuery();

Query returns 0 elements.

I tried to get all elements and with CamlQuery.CreateAllItemsQuery(); - and in date I see correct count in list data, but FieldValues in elements look like this: Screenshot from VS Locals

In CAML Query Builder Tool:

   <Where>
      <IsNotNull>
         <FieldRef Name='Title' />
      </IsNotNull>
   </Where>
</Query>

Returns: Screenshot from CAML Query Builder

How to get these values correctly?

Answer 1

I think the value type should be "Lookup" then your using the id of the lookup field (ie the id of the field in the alternative list)

<Eq>
  <FieldRef Name='IDCardNumber' LookupId='TRUE'/>
  <Value Type='Lookup'>12345</Value>
</Eq>

Answer 2

ViewFields goes in View

query.ViewXml = @"<View>
                <Query>
                    <Where>
                    <Eq>
                        <FieldRef Name='IDCardNumber' LookupId='TRUE'/>
                            <Value Type='Lookup'>12345</Value>
                    </Eq>
                    </Where>
                </Query>
                <ViewFields>
                    <FieldRef Name = 'Title'/>
                    <FieldRef Name = 'IDCardNumber'/>
                </ViewFields>
                </View>
                ";