从SQL Server读取VARBINARY（MAX）到C＃

Question

I need to read data row from SQL Server 2008. The type of one of the columns is VARBINARY(MAX) . In C# I want to use out parameter to read it (and given scenario satisfies the needs mostly).

But I need to specify the parameter variable size to fill the C# variable. Here I assume that 8000 is enough... But who knows:

database.AddOutParameter(command, "vbCertificate", DbType.Binary, 8000);

So the questions are:

1. What is the size of MAX in number for SQL Server 2008?
2. Is this ok to use out parameter for this scenario?

Answer 1

The max size for VARBINARY(MAX) is 2 GB of data - 2'147'483'648 bytes.

In your case, when defining it in C#, I would recommend using int.MaxValue as the value to provide.

And yes, if you want to get the array of bytes back from the SQL Server 2008 table, then you can most definitely use an out parameter.

Answer 2

As @marc_s said, I will just want to add something.

There are two data types

binary [ ( n ) ]

Fixed-length binary data with a length of n bytes, where n is a value from 1 through 8,000. The storage size is n bytes.

varbinary [ ( n | max) ]

Variable-length binary data. n can be a value from 1 through 8,000. max indicates that the maximum storage size is 2^31-1 (equals int.MaxValue ie 2,147,483,647) bytes. The storage size is the actual length of the data entered + 2 bytes. The data that is entered can be 0 bytes in length.

if you are specifying max then your concern should be with varbinary instead of binary

database.AddOutParameter(command, "vbCertificate", DbType.Binary, 8000);

database.AddOutParameter(command, "vbCertificate", SqlDbType.VarBinary, int.MaxValue);

Answer 3

I haven't seen an explicit size anywhere for MAX. Have you tried executing this using DbType.Object? That is defined on msdn as a general type for any type not explicitly defined. I would try that and see if it works or not. Otherwise, I would probably stick to DbType.Binary as you chose.