c# - 从使用方法作为参数的方法返回字符串

Question

我有一个 SQL 模板方法，我想返回一个字符串，还有各种执行查询的方法，我想从中获取字符串:

private string sqlQueryReturnString(Action<SqlConnection> sqlMethod)
{
    string result = "";
    SqlConnection conn = new SqlConnection();
    conn.ConnectionString = ConfigurationManager.ConnectionStrings["ApplicationServices"].ConnectionString;
    try
    {
        //open SQL connection
        conn.Open();
        result = sqlMethod(conn);
    }
    catch (Exception ex)
    {
        System.Diagnostics.Debug.Write(ex.ToString());
    }
    finally
    {
        conn.Close();
    }
    return result;
}

//Get the primary key of the currently logged in user
private string getPKofUserLoggedIn(SqlConnection conn)
{
    int result = 0;
    SqlCommand getPKofUserLoggedIn = new SqlCommand("SELECT [PK_User] FROM [User] WHERE [LoginName] = @userIdParam", conn);
    //create and assign parameters
    getPKofUserLoggedIn.Parameters.AddWithValue("@userIdParam", User.Identity.Name);
    //execute command and retrieve primary key from the above insert and assign to variable
    result = (int)getPKofUserLoggedIn.ExecuteScalar();
    return result.ToString();
}

以上是我认为的处理方式。这将是电话:

string test = sqlQueryReturnString(getPKofUserLoggedIn);

这部分不工作:

result = sqlMethod(conn);

看来 sqlMethod 被假定为无效。

我该怎么做才能获得我想要的功能？

Answer 1

你想要一个 Func<SqlConnection, string> . Action用于 void方法，Func对于返回某些东西的方法。