我是Neo4j的C＃开发人员。我花了几周时间学习图形概念并试用Cypher。这是一个很好的经历！
我现在尝试通过官方C＃驱动程序处理代码中的一些实际数据。我很惊讶地发现驱动程序只是API的包装器，顶部没有真正的.Net功能。
在创建节点时，我设法使用这种模式创建了Cypher语句：
CREATE (:Movie {tmdbId: {tmdbId}, imdbId: {imdbId}, title: {title}, originalTitle: {originalTitle}, collectionInfo: {collectionInfo}, genres: {genres}, releaseDate: {releaseDate}, plot: {plot}, tagline: {tagline}, originalLanguage: {originalLanguage}, tmdbPopularity: {tmdbPopularity}, tmdbVoteAverage: {tmdbVoteAverage}, tmdbVoteCount: {tmdbVoteCount}, budget: {budget}} )
从对象自动生成参数集合。它工作正常。但是在创建关系时我会遇到意外错误。
这是我用来创建关系的声明。通过Id查找源节点和目标节点。
MATCH (s:Person), (t:Movie) WHERE s.personId=35742 AND t.movieId=19404 CREATE (s)-[r:ACTED_IN {order: {order}, character: {character}}]->(t) RETURN r
我收到的错误是：
System.Reflection.TargetParameterCountException: 'Parameter count mismatch.'
参数集合的创建方式与上次相同。它按预期保存了两个名为“order”和“character”的属性。
我遗失的陈述中是否有错误？
/// <summary>
/// Add object as node in Neo4j database.
/// All public properties will automatically be added as properties of the node.
/// </summary>
/// <param name="obj">Generic POCO object</param>
/// <param name="label">Specify type name to be uses. Skip if you are satisfied with object type name.</param>
public void AddNode(object obj, string label = null)
{
using (var session = _driver.Session())
{
label = label ?? obj.GetType().Name;
var parameters = GetProperties(obj);
var valuePairs = string.Join(", ", parameters.Select(p => $"{p.Key}: {{{p.Key}}}"));
var statement = $"CREATE (:{label} {{{valuePairs}}} )";
var result = session.Run(statement, parameters);
Debug.WriteLine($"{result.Summary.Counters.NodesCreated} {label} node created with {result.Summary.Counters.PropertiesSet} properties");
}
}
public void AddRelation(string sourceNodeName, string sourceIdName, string targetNodeName, string targetIdName, string relationName, object relation, string relationSourceIdName, string relationPropertyIdName)
{
using (var session = _driver.Session())
{
//MATCH(s:Person), (t:Person)
//WHERE s.name = 'Source Node' AND t.name = 'Target Node'
//CREATE(s) -[r:RELTYPE]->(t)
//RETURN r
var parameters = GetProperties(relation);
var sourceId = parameters[relationSourceIdName];
var targetId = parameters[relationPropertyIdName];
var properties = parameters.Where(p => p.Key != relationSourceIdName && p.Key != relationPropertyIdName).ToList();
var valuePairs = string.Join(", ", properties.Select(p => $"{p.Key}: {{{p.Key}}}"));
var statement = $"MATCH (s:{sourceNodeName}), (t:{targetNodeName}) WHERE s.{sourceIdName}={sourceId} AND t.{targetIdName}={targetId} CREATE (s)-[r:{relationName} {{{valuePairs}}}]->(t) RETURN r";
var result = session.Run(statement, properties);
Debug.WriteLine($"{result.Summary.Counters.RelationshipsCreated} {relationName} relations created with {result.Summary.Counters.PropertiesSet} properties");
}
}
private static Dictionary<string, object> GetProperties(object obj)
{
var dictionary = new Dictionary<string, object>();
foreach (var property in obj.GetType().GetProperties())
{
var propertyName = property.Name;
var value = property.GetValue(obj);
var array = value as string[];
if (array != null)
{
value = string.Join(",", array);
}
if (value is DateTime)
{
var dateTime = (DateTime)value;
value = dateTime.ToString("yyyy-MM-dd");
}
dictionary.Add(propertyName.ToCamelCase(), value);
}
return dictionary;
}
答案 0 :(得分：0)
调整后的工作方法现在如下所示：
public void AddRelation(string fromNodeName, string fromIdName, string toNodeName, string toIdName, string relationName, object relation, string relationFromIdName, string relationToIdName)
{
using (var session = _driver.Session())
{
//MATCH(s:Person), (t:Person)
//WHERE s.name = 'Source Node' AND t.name = 'Target Node'
//CREATE(s) -[r:RELATIONTYPE]->(t)
//RETURN r
var parameters = GetProperties(relation);
var fromIdValue = parameters[relationFromIdName];
var toIdValue = parameters[relationToIdName];
var properties = parameters.Where(p => p.Key != relationFromIdName && p.Key != relationToIdName).ToDictionary(p => p.Key, p => p.Value);
var valuePairs = string.Join(", ", properties.Select(p => $"{p.Key}: {{{p.Key}}}"));
var statement = $"MATCH (s:{fromNodeName}), (t:{toNodeName}) WHERE s.{fromIdName}={fromIdValue} AND t.{toIdName}={toIdValue} CREATE (s)-[r:{relationName} {{{valuePairs}}}]->(t) RETURN r";
var result = session.Run(statement, properties);
Console.WriteLine($"{result.Summary.Counters.RelationshipsCreated} {relationName} relations created with {result.Summary.Counters.PropertiesSet} properties");
}
}