Informix（C＃）：如何正确设置/取消设置Blob字段？

Update mytable set myblobcolumn = ? where myid = 1;

using (IfxConnection conn = GetIfxConnection())
using (IfxCommand cmd = new IfxCommand(updateSql, conn))
{
    var param = new IfxParameter(\"myblobcolumn\", IfxType.Blob) { IsNullable = true };
    cmd.Parameters.Add(param).Value = DBNull.Value

    cmd.ExecuteNonQuery(); //ERROR [HY000] [Informix .NET provider][Informix]Illegal attempt to use Text/Byte host variable.
}

IfxBlob

DBNull.Value

UPDATE mytable SET myblobcolumn = ?::byte WHERE myid = 1;

DBNull.Value

UPDATE mytable SET myblobcolumn = ?::blob WHERE myid = 1;

var param = new IfxParameter { ParameterName = \"myblobcolumn\" }

UPDATE mytable SET myblobcolumn = ? where myid = 1;

using (IfxConnection conn = GetIfxConnection())
using (IfxCommand cmd = new IfxCommand(updateSql, conn))
{
    var param = new IfxParameter { ParameterName = \"myblob\" }
    cmd.Parameters.Add(param);

    var value = GetSomeValue();

    if (value is Byte[])
        cmd.Paremeters[\"myblob\"].Value = GetIfxBlob(value);
    else
        cmd.Parameters[\"myblob\"].Value = DBNull.Value;

    //...
}