带有 byte[] 字段的 DataTable 作为存储过程的参数 [英] DataTable with a byte[] field as parameter to a stored procedure

问题描述

我一直在重复使用这种使用 DataTable 作为存储过程参数的方法，并且效果很好.这是简化的工作代码:

I've been reusing this method of using a DataTable as a parameter to a stored procedure and it's been working great. This is the simplified working code:

using (dbEntities dbe = new dbEntities())
{
    var dt = new dataTable();
    dt.Columns.Add("ID");
    dt.Columns.Add("Message");
    dt.Columns.Add("CreatedOn", typeof(DateTime));

    foreach (var row in randomDataSource)
    {
        dt.Rows.Add(
            row.id,
            row.message,
            DateTime.Now
            );
    }

    var tableType = new SqlParameter("tableType", SqlDbType.Structured);
    tableType.Value = dt;
    tableType.TypeName = "[dbo].[RandomTableType]";

    dbe.ExecuteStoreCommand(
        "EXEC [dbo].[SaveTable] @tableType",
        new object[] { tableType }
        );
}

当我要添加的字段是二进制类型时，就会出现问题.即:

The problem arises when the field I want to add is of a binary type. i.e.:

dt.Columns.Add("BinaryMessage", typeof(byte[]));

顺便说一下，数据库中对应的列是varbinary(MAX).当我尝试运行此程序时，出现此错误:

The corresponding column in the database is varbinary(MAX) by the way. When I try to run this, I get this error:

从数据类型 nvarchar(max) 到 varbinary(max) 的隐式转换是不允许.使用 CONVERT 函数运行此查询.

Implicit conversion from data type nvarchar(max) to varbinary(max) is not allowed. Use the CONVERT function to run this query.

我如何修改我必须做的工作?

How do I modify what I have to make this work?

推荐答案

.NET 中二进制字符串的表示是 SqlBinary 结构.

The representation for a binary string in .NET is the SqlBinary structure.

你想像这样添加你的列:

You want to add your column like this:

dt.Columns.Add("BinaryMessage", typeof(SqlBinary));

SqlBinary 类有一个 显式转换为字节数组和隐式转换一个字节数组，因此从字节数组到列的值是一个简单的赋值问题，而从列中获取字节数组需要显式转换.

The SqlBinary class has an explicit conversion to a byte array and an implicit conversion from a byte array, so the value from a byte array to the column is a simple matter of assignment, while getting a byte array from the column requires an explicit cast.

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