如何使用 SQLite-Net Extensions 进行低 level/plain SQL 查询?

How to make low level/plain SQL queries with SQLite-Net Extensions?

我正在使用 SQLite-Net Extensions,我想在对它进行一些操作之前检查 table 是否存在。这是我试过的:

await this.database.ExecuteScalarAsync<int>("SELECT count(*) FROM sqlite_master WHERE type='table' AND name='{0}'", tableName).ContinueWith( t =>
{
    System.Diagnostics.Debug.WriteLine(t.Result);
});

输出为0。如果我直接在数据库上查询它,我会得到一个结果 (1)。然后我试了

var tableQuery = string.Format("SELECT name FROM sqlite_master WHERE type='table' AND name='{0}'", tableName);
var result = await this.database.ExecuteAsync(tableQuery);

我得到一个例外:

SQLite.SQLiteException: Row
  at SQLite.SQLiteCommand.ExecuteNonQuery () [0x0009b] in /Users/fak/Dropbox/Projects/sqlite-net/src/SQLite.cs:2172 
  at SQLite.SQLiteConnection.Execute (System.String query, System.Object[] args) [0x00040] in /Users/fak/Dropbox/Projects/sqlite-net/src/SQLite.cs:659 
  at SQLite.SQLiteAsyncConnection+<ExecuteAsync>c__AnonStorey9.<>m__0 () [0x00013] in /Users/fak/Dropbox/Projects/sqlite-net/src/SQLiteAsync.cs:222 
  at System.Threading.Tasks.Task`1[TResult].InnerInvoke () [0x0000f] in <d18287e1d683419a8ec3216fd78947b9>:0 
  at System.Threading.Tasks.Task.Execute () [0x00010] in <d18287e1d683419a8ec3216fd78947b9>:0 
  at App.Database+<ClearTable>d__63.MoveNext () [0x00069] in xxx\Database.cs:1011 
  at App.Util.Helper+<CleanUpTemporaryFiles>d__8.MoveNext () [0x0013a] in xxx\Helper.cs:200 
  at App.Pages.DetailPage+<OnDisappearing>d__23.MoveNext () [0x000b1] in xxx\DetailPage.xaml.cs:449 

对于 QueryAsync 你需要一个带有无参数构造函数的对象。

现在我不知道如何进行简单的 SELECT 查询。是否还有一种方法可以获得比 Row 更详细的异常消息?

您将参数传递给 SQL 的方式不正确。根据 the docs,而不是

AND name='{0}'

你应该使用:

name = ?