NHibernate ignores length attribute

问题

After running SQL Profiler, I realized that NHibernate was mapping strings to nvarchar(4000). I fixed it by specifying type=AnsiString and length=... in the hbm file. It is now generating varchar(8000) statements, and it is ignoring the length. How come?!

hbm file:

<property name="EmailAddress" column="EMAIL_ADDRESS" type="AnsiString" length="120" />

database field:

[EMAIL_ADDRESS] [varchar](120) NULL,

TIA

回答1:

Actually in previous versions of nhibernate the check against length was implemented also for query creation.

But, the current implementation of the SqlDriver got a change last year, see https://nhibernate.jira.com/browse/NH-3036 for details of the fix.

Bugfix:

    // Used from SqlServerCeDriver as well
    public static void SetVariableLengthParameterSize(IDbDataParameter dbParam, SqlType sqlType)
    {
        SetDefaultParameterSize(dbParam, sqlType);

        // no longer override the defaults using data from SqlType, since LIKE expressions needs larger columns
        // https://nhibernate.jira.com/browse/NH-3036
        //if (sqlType.LengthDefined && !IsText(dbParam, sqlType) && !IsBlob(dbParam, sqlType))
        //{
        //  dbParam.Size = sqlType.Length;
        //}

        if (sqlType.PrecisionDefined)
        {
            dbParam.Precision = sqlType.Precision;
            dbParam.Scale = sqlType.Scale;
        }
    }

The defaults are what you see (4000/8000) dependent on the data type...

来源：https://stackoverflow.com/questions/20111457/nhibernate-ignores-length-attribute