Question

I have these two exceptions generated when I try to get data from SQL database in C#:

System.Data.SqlClient.SqlException: Transaction (Process ID 97) was deadlocked on lock resources with another process and has been chosen as the deadlock victim.

OR

System.Data.SqlClient.SqlException: Transaction (Process ID 62) was deadlocked on lock resources with another process and has been chosen as the deadlock victim.

OR

System.Data.SqlClient.SqlException: Transaction (Process ID 54) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction.

this is the code:

 using (SqlConnection con = new SqlConnection(datasource))
 {
    SqlCommand cmd = new SqlCommand("Select * from MyTable Where ID='1' ", con);
    cmd.CommandTimeout = 300;
    con.Open();
    SqlDataAdapter adapter = new SqlDataAdapter(cmd);
    DataSet ds = new DataSet();
    adapter.Fill(ds);
    con.Close();
    return ds.Tables[0];
 }

These happened every time.

Any ideas on how these can be resolved?

Answer 1

Not that this is going to help the deadlock issue, but you should be disposing your other IDisposable objects much like you’re disposing your SqlConnection as such:

    using (SqlConnection con = new SqlConnection(datasource))
    using (SqlCommand cmd = new SqlCommand("Select * from MyTable Where ID='1' ", con))
    {
        cmd.CommandTimeout = 300;
        con.Open();
        using (SqlDataAdapter adapter = new SqlDataAdapter(cmd))
        using (DataSet ds = new DataSet())
        {
            adapter.Fill(ds);
            return ds.Tables[0];
        }
    }

You might be able to avoid the lock with a locking hint in your query thusly:

Select * from MyTable with (nolock) Where ID='1'

I want to be clear though, you’re allowing for reads of uncommitted data with this solution. It’s a risk in a transactional system. Read this answer. Hope this helps.