How does one make NHibernate stop using nvarchar(4000) for insert parameter strings?

Specify the Type as NHibernateUtil.AnsiString with a Length instead of using a CustomSqlType.

This issue can cause a huge performance problem in queries if it forces SQL Server to perform a table scan instead of using an index. We use varchar throughout our database so I created a convention to set the type globally:

/// <summary>/// Convert all string properties to AnsiString (varchar). This does not work with SQL CE./// </summary>public class AnsiStringConvention : IPropertyConventionAcceptance, IPropertyConvention{    public void Accept(IAcceptanceCriteria<IPropertyInspector> criteria)    {        criteria.Expect(x => x.Property.PropertyType.Equals(typeof(string)));    }    public void Apply(IPropertyInstance instance)    {        instance.CustomType("AnsiString");    }}

Okay this is what we have to do, the SQLClientDriver ignores the length property of the SqlType. So we created a our own driverclass inheriting from SQLClientDriver and override the method GenerateCommand...Something like this:

public override IDbCommand GenerateCommand(CommandType type, NHibernate.SqlCommand.SqlString sqlString, SqlType[] parameterTypes){    var dbCommand = base.GenerateCommand(type, sqlString, parameterTypes);    SetParameterSizes(dbCommand.Parameters, parameterTypes);    return dbCommand;}private static void SetParameterSizes(IDataParameterCollection parameters, SqlType[] parameterTypes){    for (int index = 0; index < parameters.Count; ++index)        SetVariableLengthParameterSize((IDbDataParameter)parameters[index], parameterTypes[index]);}private static void SetVariableLengthParameterSize(IDbDataParameter dbParam, SqlType sqlType){    SetDefaultParameterSize(dbParam, sqlType);    if (sqlType.LengthDefined && !IsText(dbParam, sqlType) && !IsBlob(dbParam, sqlType))        dbParam.Size = sqlType.Length;    if (!sqlType.PrecisionDefined)        return;    dbParam.Precision = sqlType.Precision;    dbParam.Scale = sqlType.Scale;}