byte[] as PK

[Mircea Pleteriu]

Hi All,

byte[] b1 = Guid.NewGuid().ToByteArray();
byte[] b2 = Guid.NewGuid().ToByteArray();

DataTable dt = new DataTable();
dt.Columns.Add("C1", typeof(byte[]));
dt.PrimaryKey = new DataColumn[] {dt.Columns["C1"]};

dt.Rows.Add(new object[] {b1});
dt.Rows.Add(new object[] {b2});

This code throws the exception shown below. Does anyone know why?

Unhandled Exception: System.Data.ConstraintException: Column 'C1' is
constrained
to be unique. Value 'System.Byte[]' is already present.
at System.Data.DataTable.InsertRow(DataRow row, Int32 proposedID, Int32
pos)
at System.Data.DataRowCollection.Add(Object[] values)
at ConsoleApplication1.Class1.Main(String[] args) in d:\projects
development\
c#\test\consoleapplication1\consoleapplication1\class1.cs:line 34

 

[Mircea Pleteriu]

I've found the reason at

http://www.dotnet247.com/247reference/msgs/47/238334.aspx

 

[Mark Ashton]

In V2.0, DataSet can support byte[] as a primary key but it has issues with
byte[] are mutable given that you can change the value without the dataset
being aware of it - causes indexing issues. The DataSet could make a copy
of the byte[], but that isn't happening. You would need to replace the
byte[] object rather than just edit the value.

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I've found the reason at

http://www.dotnet247.com/247reference/msgs/47/238334.aspx

Hi All,

byte[] b1 = Guid.NewGuid().ToByteArray();
byte[] b2 = Guid.NewGuid().ToByteArray();

DataTable dt = new DataTable();
dt.Columns.Add("C1", typeof(byte[]));
dt.PrimaryKey = new DataColumn[] {dt.Columns["C1"]};

dt.Rows.Add(new object[] {b1});
dt.Rows.Add(new object[] {b2});

This code throws the exception shown below. Does anyone know why?

Unhandled Exception: System.Data.ConstraintException: Column 'C1' is
constrained
to be unique. Value 'System.Byte[]' is already present.
at System.Data.DataTable.InsertRow(DataRow row, Int32 proposedID,
Int32
pos)
at System.Data.DataRowCollection.Add(Object[] values)
at ConsoleApplication1.Class1.Main(String[] args) in d:\projects
development\
c#\test\consoleapplication1\consoleapplication1\class1.cs:line 34

 

[Miha Markic [MVP C#]]

Hi Mircea,

Why would you want to use byte[] as PK at all?