运算符'!='不能应用于'Task'和'int'类型的操作数

Question

最近我开始使用Xamarin创建Android应用程序.我尝试用SQLite创建一个小型本地数据库.我使用了Xamarin文档网站上的以下教程.

不幸的是我收到一个错误:

错误CS0019:运算符'!='不能应用于'Task'和'int'类型的操作数(CS0019)

我的代码如下:

private string createDatabase(string path)
    {
        try
        {
            var connection = new SQLiteAsyncConnection(path);{
                connection.CreateTableAsync<Person>();
                return "Database created";
            }
        }
        catch (SQLiteException ex)
        {
            return ex.Message;
        }
    }

    private string insertUpdateData(Person data, string path)
    {
        try
        {
            var db = new SQLiteAsyncConnection(path);
            if ( db.InsertAsync(data) != 0)
                db.UpdateAsync(data);
            return "Single data file inserted or updated";
        }
        catch (SQLiteException ex)
        {
            return ex.Message;
        }
    }

    private int findNumberRecords(string path)
    {
        try
        {
            var db = new SQLiteConnection(path);
            // this counts all records in the database, it can be slow depending on the size of the database
            var count = db.ExecuteScalar<int>("SELECT Count(*) FROM Person");

            // for a non-parameterless query
            // var count = db.ExecuteScalar<int>("SELECT Count(*) FROM Person WHERE FirstName="Amy");

            return count;
        }
        catch (SQLiteException ex)
        {
            return -1;
        }
    }

Person类如下:

using System;
using SQLite;

namespace HelloWorld {
public class Person
{
    [PrimaryKey, AutoIncrement]
    public int ID { get; set; }

    public string FullName { get; set; }

    public string CarLicense { get; set; }

    public override string ToString()
    {
        return string.Format("[Person: ID={0}, FullName={1}, CarLicense={2}]", ID, FullName, CarLicense);
    }
}
}

任何人都可以帮我解决这个错误吗？

Answer 1

你可以这样做:

if ( (await db.InsertAsync(data)) != 0)

另请参阅此答案,了解为什么await通常优先使用.Result.