错误是什么（不是所有路径都返回一个值） [英] What is the problem error is (not all paths return a value)

问题描述

public Stream DownloadFile()
        {
            using (SqlConnection con = new SqlConnection("GAPDB"))
            {
                using (SqlCommand cmd = new SqlCommand("SELECT FileUpload FROM [FirmWareVersion]", con))
                {
                    con.Open();

                    SqlDataReader reader = cmd.ExecuteReader();

                    if (reader.Read())
                    {
                        byte[] data = (byte[])reader["FileUpload"];
                        System.IO.MemoryStream ms = new System.IO.MemoryStream(data);

                    }
                    
                }
            }

        }

我尝试了什么：



首先我认为这是一个连接字符串但不是我需要一些帮助请

What I have tried:

first i thought it was an connection string but not that i need some help please

推荐答案

你的方法应该返回一个 Stream 类型的变量，但是我无处可见 return 在你的代码中...

尝试这样的事情：

Your method should return a variable of Stream type, but nowhere I can see a return in your code...
Try something like this:

public Stream DownloadFile()
{
	using (SqlConnection con = new SqlConnection("GAPDB"))
	{
		using (SqlCommand cmd = new SqlCommand("SELECT FileUpload FROM [FirmWareVersion]", con))
		{
			con.Open();

			SqlDataReader reader = cmd.ExecuteReader();

			if (reader.Read())
			{
				byte[] data = (byte[])reader["FileUpload"];
				System.IO.MemoryStream ms = new System.IO.MemoryStream(data);
				
				return( ms ); // return it...
			}
		}
	}
	
	return( null ); // return null as sign of failure...
}

错误说不是所有路径都返回一个值。那么，为什么编译器认为你的代码需要返回一个值呢？因为你如何声明这个方法。你告诉编译器你的方法将返回一个Stream。但是你没有任何返回Stream的代码。

The error says that "not all paths return a value." So, why does the compiler think your code needs to return a value? Because of how you declared this method. You told the compiler that your method will be returning a Stream. But you do not have any code that returns a Stream.

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