How I can store and get correct Guid from database?

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Hi All,

I am working on ASP.Net,C# web application with MySql Database...
for DAL(Data Access Layer) I am using Entity Framework and Linq...
I am having a db table with Column ProcessId(DataType - binary(16)) to store Guid..

while inserting data into database table ...it's taking ProcessId = '9e5ba38f-cfb0-4dcb-8365-c4536acb7272' (which is generated by Guid.newGuid();)
and while fetching same record from table it's giving me some diff. ProcessId
why is it so? How I can store and get correct Guid from database?

Looking out for urgent reply....Please

Posted 7-Jul-15 3:47am

Ravindra Chandak

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Kornfeld Eliyahu Peter 7-Jul-15 10:07am

It seems to me that you are storing a string representation of the GUID into the database and not a binary value...
Tty to send it as byte array - https://msdn.microsoft.com/en-us/library/system.guid.tobytearray(v=vs.110).aspx

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cybie04 · Answer 1 · 2015-07-07T19:30:00

If conversion to binary fails for some reason you could try to use the sql server type uniqueidentifier. Maybe you're more lucky then.

Since we speak about MySQL this might not be an option afterall.
Instead on the .NET part you should make sure the GUID is converted accordingly.

For .NET Guid-type values generated via Guid.NewGuid() you can pass them to a MySqlCommand Parameter if you cast the guid value as Byte Array.
This can be done via Guid.ToByteArray() as mentioned below:

C#

string connectionString = string.Format("Server={0};Database={1};Uid={2};pwd={3}", "server", "database", "user", "password");

Guid orgId = Guid.NewGuid();
Guid fromDb = Guid.Empty;

using (MySqlConnection conn = new MySqlConnection(connectionString))
{
    conn.Open();

    //How to insert .NET GUID into MySQL
    using (MySqlCommand cmd = new MySqlCommand("INSERT INTO test (id) VALUES (?id)", conn))
    {
        cmd.Parameters.Add("id", MySqlDbType.Binary).Value = orgId.ToByteArray();
        cmd.ExecuteNonQuery();
    }

    //How to retrieve GUID-Value from MySQL
    using (MySqlCommand cmd = new MySqlCommand("SELECT id FROM test", conn))
    {
        using (MySqlDataReader r = cmd.ExecuteReader())
        {
            r.Read();
            fromDb = new Guid((byte[])r.GetValue(0));
        }
    }
}