C# 系统.FormatException : Input string was not in a correct format

Question

我正在尝试使用 String.Format 创建一个字符串并添加参数。但由于某种原因，我收到了错误 -

System.FormatException: Input string was not in a correct format.

这是我的代码

string queryPattern =
"PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> " +
"PREFIX db: <http://dbpedia.org/ontology/> " +
"PREFIX prop: < http://dbpedia.org/property/> " +
"SELECT ?movieLink ?title ?genreLink ?genre ?releaseDate " +
"WHERE { " +
    "?movieLink rdf:type db:Film; " +
                "foaf:name ?title. " +
    "OPTIONAL { ?movieLink prop:genre ?genreLink. " +
                "?genreLink rdfs:label ?genre. " +
                "FILTER(lang(?genre) = 'en') }. " +
    "OPTIONAL{ ?movieLink <http://dbpedia.org/ontology/releaseDate> ?releaseDate }. " +

    "{0}" +
    "{1}" +
    "FILTER(lang(?title) = 'en') " +
"}" +
"ORDER BY DESC(?releaseDate)" +
"{2}";

return String.Format(queryPattern, genreMatch, dateMatch, limit);

如有任何帮助，我们将不胜感激。

Answer 1

string.Format 使用花括号 ({}) 来指示占位符。您的格式字符串无效，因为它包含另外几个花括号。

你需要通过将它们加倍来转义这些括号:

string s = "Teststring {{ {0} }}";
string r = string.Format(s, 42);

在 r 中的结果:

Teststring { 42 }

---

例如你的行

"WHERE { " +

应该是

"WHERE {{ " +