For input parameters, the value is bound to the System.Data.Common.DbCommand that is sent to the server. For output and return value parameters, the value is set on completion of the System.Data.Common.DbCommand and after the System.Data.Common.DbDataReader is closed.

When you send a null parameter value to the server, you must specify DBNull, not null. The null value in the system is an empty object that has no value. DBNull is used to represent null values.

If the application specifies the database type, the bound value is converted to that type when the provider sends the data to the server. The provider tries to convert any type of value if it supports the IConvertible interface. Conversion errors may result if the specified type is not compatible with the value.

The DbParameter.DbType property can be inferred by setting the Value.

The DbParameter.Value property is overwritten by DbDataAdapter.Update.