没有给定的参数对应于所需的形式参数 - .NET 错误

Question

我一直在重构我的一个旧 MSSQL 连接帮助程序库，但出现以下错误：

Error CS7036 There is no argument given that corresponds to the required formal parameter 'errorMsg' of 'ErrorEventArg.ErrorEventArg(string, string)' MSSQLTest C:\Users\Administrator\Desktop\MSSQLTest\MSSQLTest\MSSQLConnection.cs 61

到目前为止，这是我的代码：

MSSQLConnection.cs

using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Threading;

namespace MSSQLTest
{
    public class ErrorEventArg : EventArgs
    {
        public string ErrorMsg { get; set; }
        public string LastQuery { get; set; }

        public ErrorEventArg(string errorMsg, string lastQuery)
        {
            ErrorMsg = errorMsg;
            LastQuery = lastQuery;
        }
    }

    public class MSSQLConnection
    {
        /// <summary>
        /// Private class objects.
        /// </summary>
        private SqlConnection sqlConnection;
        private int sqlCommandTimeout;
        private string lastQuery = string.Empty;

        /// <summary>
        /// Public event related objects & handler.
        /// </summary>
        public event ErrorHandler OnError;
        public delegate void ErrorHandler(MSSQLConnection sender, ErrorEventArg e);

        /// <summary>
        /// Class constructor.
        /// </summary>
        /// <param name="sqlConnection"></param>
        /// <param name="sqlCommandTimeout"></param>
        public MSSQLConnection(SqlConnection sqlConnection, Int32 sqlCommandTimeout = 120)
        {
            if (null == sqlConnection)
                throw new Exception("Invalid MSSQL Database Conection Handle");

            if (sqlConnection.State != System.Data.ConnectionState.Open)
                throw new Exception("MSSQL Database Connection Is Not Open");

            this.sqlConnection = sqlConnection;
            this.sqlCommandTimeout = sqlCommandTimeout;
        }

        /// <summary>
        /// Helper method to emit a database error to event subscribers.
        /// </summary>
        /// <param name="errorMsg"></param>
        internal void EmitError(String errorMsg)
        {
            var errorDelegate = OnError;
            if (errorDelegate != null)
            {
                errorDelegate(this, new ErrorEventArg() // Line #61
                {
                    ErrorMsg = errorMsg,
                    LastQuery = lastQuery
                });
            }
        }
        
        /// rest of the code snipped
    }
}

这个错误是什么意思，我该如何解决？我以前没见过这个错误...

Answer 1

您有一个带有 2 个参数的构造函数。你应该这样写：

new ErrorEventArg(errorMsv, lastQuery)

它的代码更少，更易于阅读。

编辑

或者，为了您的工作方式，您可以尝试为 ErrorEventArg 编写一个没有参数的默认构造函数，如下所示：

public ErrorEventArg() {}

Answer 2

当构造函数所需的属性之一不是 public 时，我收到此错误。如果是这种情况，请确保构造函数中的所有参数都转到 public 的属性：

使用语句命名空间 someNamespace

public class ExampleClass {

  //Properties - one is not visible to the class calling the constructor
  public string Property1 { get; set; }
  string Property2 { get; set; }

   //Constructor
   public ExampleClass(string property1, string property2)
  {
     this.Property1 = property1;
     this.Property2 = property2;  //this caused that error for me
  }
}

Answer 3

在

的构造函数中

public class ErrorEventArg : EventArgs

您必须按如下方式添加“基础”：

public ErrorEventArg(string errorMsg, string lastQuery) : base (string errorMsg, string lastQuery)
{
    ErrorMsg = errorMsg;
    LastQuery = lastQuery;
}

Answer 4

我遇到了同样的错误，但这是因为我没有创建默认构造函数。如果您还没有尝试过，请像这样创建默认构造函数：

public TestClass()
{
}

Answer 5

我在以下关于 DailyReport 的 Linq 语句中收到了同样的错误。问题是 DailyReport 没有默认构造函数。显然，它在填充属性之前实例化对象。

var sums = reports
    .GroupBy(r => r.CountryRegion)
    .Select(cr => new DailyReport
    {
        CountryRegion = cr.Key,
        ProvinceState = "All",
        RecordDate = cr.First().RecordDate,
        Confirmed = cr.Sum(c => c.Confirmed),
        Recovered = cr.Sum(c => c.Recovered),
        Deaths = cr.Sum(c => c.Deaths)
    });

Answer 6

public ErrorEventArg(string errorMsg, string lastQuery)
    : base (errorMsg, lastQuery)
{
    ErrorMsg = errorMsg;
    LastQuery = lastQuery;
}

要调用基础构造函数，sub class 和 base class 的参数必须相同。

没有给定的参数对应于所需的形式参数 - .NET 错误

There is no argument given that corresponds to the required formal parameter - .NET Error

.net

c#

.net-4.5