C# 将文件转换为字节数组，保存在Access DB中，从DB读取并创建文件

你好，

我正在努力

将文件转换为字节[]

在Access数据库中写入字节[]

从数据库中读取字节[]

从中重新创建文件

一,

二,

三,

        DataTable table = AccessConnector.GetFileByteArrayByID(122);
        DataRow row = table.Rows[0];

        System.Text.UTF8Encoding enc = new System.Text.UTF8Encoding();

        byte[] newbytes = enc.GetBytes(row.ItemArray[0].ToString());

四,

            System.IO.File.WriteAllBytes(@"C:\Users\user\Documents\Docs\a.pdf", newbytes);

问题是，新字节比字节小得多，新文件不可访问。Access DB单元格中的字符类似于中文字母。我已经尝试使用其他编码。没有什么。任何人都可以解释为什么它要小得多（23000到400个字符）。谢谢

更新为其他功能添加了代码

    public static DataTable GetFileByteArrayByID(int aID)
    {
        conn.Open();

        dbCommand = new OleDbCommand("SELECT Datei FROM Belege WHERE (ID = @ID)", conn);

        dbCommand.Parameters.Add("@ID", OleDbType.Integer).Value = aID;
        dbDataAdapter = new OleDbDataAdapter(dbCommand);
        DataTable resultDataTable = new DataTable();
        dbDataAdapter.Fill(resultDataTable);

        conn.Close();
        return resultDataTable;
    }

您从未为

@文件

参数赋值

此外，在读取数据时不需要转换为字符串，这应该可以：

byte[] newbytes = (byte[])table.Rows[0][0];

---

解决方案

    public static void WriteByteArrayToID(int aID, byte[] aFile)
    {
        conn.Open();

        dbCommand = new OleDbCommand("UPDATE Belege SET Datei = @file WHERE(ID = @ID)", conn);

        string tmp = Convert.ToBase64String(aFile);

        dbCommand.Parameters.Add("@file", OleDbType.VarChar).Value = tmp;
        dbCommand.Parameters.Add("@ID", OleDbType.Integer).Value = aID;

        dbDataAdapter = new OleDbDataAdapter(dbCommand);
        dbCommand.ExecuteNonQuery();

        conn.Close();
    }

    public static DataTable GetFileByteArrayByID(int aID)
    {
        conn.Open();

        dbCommand = new OleDbCommand("SELECT Datei FROM Belege WHERE (ID = @ID)", conn);

        dbCommand.Parameters.Add("@ID", OleDbType.Integer).Value = aID;
        dbDataAdapter = new OleDbDataAdapter(dbCommand);
        DataTable resultDataTable = new DataTable();
        dbDataAdapter.Fill(resultDataTable);

        conn.Close();
        return resultDataTable;
    } 

        //-----------------------------------------------------------------------------------------------------------------

        byte[] bytes = System.IO.File.ReadAllBytes(@"C:\Users\user\Music\1.pdf");

        AccessConnector.WriteByteArrayToID(122, bytes);

        DataTable table = AccessConnector.GetFileByteArrayByID(122);

        string file = table.Rows[0][0] as string;

        System.IO.File.WriteAllBytes(@"C:\Users\user\Documents\Dokumente\a.pdf", Convert.FromBase64String(file));

        //-----------------------------------------------------------------------------------------------------------------

---

1.是的，谢谢你。我没看到…：D 2。他说：如果我写

byte[]newbytes=（byte[]）表，就不能从字符串转换为byte[]，行[0][0]

在这种情况下，到字符串的转换可能已经在

GetFileByteArrayByID（…）

方法中发生。我觉得您的代码不错，但不幸的是，我已经很久没有使用access数据库了，

Datei

列是什么数据类型？它应该类似于“二进制”。

dbCommand.Parameters.Add("@ID", OleDbType.Integer).Value = aID;
dbCommand.Parameters.Add("@ID", OleDbType.VarBinary).Value = aFile;

byte[] newbytes = (byte[])table.Rows[0][0];

    public static void WriteByteArrayToID(int aID, byte[] aFile)
    {
        conn.Open();

        dbCommand = new OleDbCommand("UPDATE Belege SET Datei = @file WHERE(ID = @ID)", conn);

        string tmp = Convert.ToBase64String(aFile);

        dbCommand.Parameters.Add("@file", OleDbType.VarChar).Value = tmp;
        dbCommand.Parameters.Add("@ID", OleDbType.Integer).Value = aID;

        dbDataAdapter = new OleDbDataAdapter(dbCommand);
        dbCommand.ExecuteNonQuery();

        conn.Close();
    }

    public static DataTable GetFileByteArrayByID(int aID)
    {
        conn.Open();

        dbCommand = new OleDbCommand("SELECT Datei FROM Belege WHERE (ID = @ID)", conn);

        dbCommand.Parameters.Add("@ID", OleDbType.Integer).Value = aID;
        dbDataAdapter = new OleDbDataAdapter(dbCommand);
        DataTable resultDataTable = new DataTable();
        dbDataAdapter.Fill(resultDataTable);

        conn.Close();
        return resultDataTable;
    } 

        //-----------------------------------------------------------------------------------------------------------------

        byte[] bytes = System.IO.File.ReadAllBytes(@"C:\Users\user\Music\1.pdf");

        AccessConnector.WriteByteArrayToID(122, bytes);

        DataTable table = AccessConnector.GetFileByteArrayByID(122);

        string file = table.Rows[0][0] as string;

        System.IO.File.WriteAllBytes(@"C:\Users\user\Documents\Dokumente\a.pdf", Convert.FromBase64String(file));

        //-----------------------------------------------------------------------------------------------------------------