Using Linq to Sql in C#, is there any way I can automatically truncate too-long data?

So, I'm importing data from one database into another. There开发者_StackOverflow中文版 are about 5,000 records (so nothing ridiculous, but not small enough to eyeball). Is there an easy way to automatically truncate data that is too long - specifically, varchar fields? I don't want truncation to be silent since the too-long fields will likely require attention, but it would be really nice if a name that is 2 characters too long wouldn't fail on insert, and throw a totally non-specific exception.

The solution I'd like to implement is one that will truncate the data, insert it, and log this. Has anyone else done something similar?

Linq2Sql will generate a property like this:

    [Column(Storage="_Name", DbType="NVarChar(50) NOT NULL")]
    public string Name
    {
        get
        {
            return this._Name;
        }
        set
        {
            if ((this._Name != value))
            {
                this.OnNameChanging(value);
                this.SendPropertyChanging();
                this._Name = value;
                this.SendPropertyChanged("Name");
                this.OnNameChanged();
            }
        }
    }

See how it calls a function called OnNameChanged? Just create a function with that name to do the truncation and logging:

void OnNameChanged()
{
    if (Name.Length > 50)
    {
        Name = Name.Substring(0, 50);
        LogSomehow("Name truncated");
    }
}

I would make an extension iterator method that you could throw inline with your query, doing something like this:

public static IEnumerable<string> Truncater(this IEnumerable<string> s, int len)
{
    foreach( var str in s )
    {
        if( str.Length > len )
        {
            string outStr = str.Substring(0, len);
            Console.WriteLine(String.Format("Truncated {0} to {1}", str, outStr));
            yield return outStr;
        }
        else
            yield return str;
    }
}

Here's a more automatic method. It looks at the type/length of each column being inserted, on the fly.

Use it like this:

            foreach (object insert in context.GetChangeSet().Inserts)
            {
                FindLongStrings(update);
            }

            context.SubmitChanges();

And here's the method: (It's horribly inefficient so I wouldn't leave it in production code, but if you've got a one-time conversion/import (and it sound like you do), it might do the trick.)

    public static void FindLongStrings(object testObject)
    {
        foreach (PropertyInfo propInfo in testObject.GetType().GetProperties())
        {
            foreach (ColumnAttribute attribute in propInfo.GetCustomAttributes(typeof(ColumnAttribute), true))
            {
                if (attribute.DbType.ToLower().Contains("varchar"))
                {
                    // kinda crude, but it works...
                    string dbType = attribute.DbType.ToLower();
                    int numberStartIndex = dbType.IndexOf("varchar(") + 8;
                    int numberEndIndex = dbType.IndexOf(")", numberStartIndex);
                    string lengthString = dbType.Substring(numberStartIndex, (numberEndIndex - numberStartIndex));
                    int maxLength = 0;
                    int.TryParse(lengthString, out maxLength);

                    string currentValue = (string)propInfo.GetValue(testObject, null);

                    // Do your logging and truncation here
                    if (!string.IsNullOrEmpty(currentValue) && currentValue.Length > maxLength)
                        Console.WriteLine(testObject.GetType().Name + "." + propInfo.Name + " " + currentValue + " Max: " + maxLength);

                }
            }
        }
    }