Question

我创建了一个带有sqlite连接的xamarin应用。当我运行此代码时，它会导致异常：

public List<string> GetTpe(string word)
    {
        return dbConnection.Query<string>("Select * From Entries Where Entries.word =?", word).ToList();
    }

这是我的课程条目：

public class Entries
{
    public Entries()
    {

    }

    public Entries(string word)
    {
        this.word = word;
    }
    public Entries(string word, string wordtype, string definition)
    {
        this.word = word;
        this.type = wordtype;
        this.defn = definition;
    }   
    public string word
    { get; set; }

    public string type
    { get; set; }

    public string sdex { get; set; }
    public int wlen { get; set; }

    public string defn
    { get; set; }

    //public List<string> Word { get; set; }


}

这是例外：System.MissingMethodException：找不到类型为'System.String'的构造方法。

请帮助。非常感谢。

Answer 1

此SQL查询返回Entries个对象，而不是string。

Query<string>("Select * From Entries Where Entries.word = ?", word)

如果您尝试仅返回string的列表，而string是记录中的一个字段，请将该字段分解为各个部分：

var entriesList = conn.Query<Entries>("Select * From Entries Where Entries.word =?", word);
var stringEnumuerationOfDefn = entriesList.Select(entries => entries.defn);
var stringListOfDefn = stringEnumuerationOfDefn.ToList();

更新：

conn.Insert(new Entries { word = "someWord", defn = "defn1", sdex = "sdex1" });
string wordFilter = "someWord";
var entriesList = conn.Query<Entries>("Select * From Entries Where Entries.word = ? ", word); // new string[1] { word });
var wordEnumueration = entriesList.Select(entries => entries.defn);
var wordList = wordEnumueration.ToList();
foreach (var word in wordList)
{
    Console.WriteLine(word)
}

缺少方法异常Xamarin

1 个答案: