Creating a CLR Table Valued Function

Question

Am trying to create a simple table valued CLR function, which takes a comma separated string as a parameter, splits it up and returns it as multiple rows

Following a few online tutorials I ended up at:

[SqlFunction(FillRowMethodName = "FillRow",TableDefinition="val nvarchar(1000)")]
public static IEnumerable SqlFunction1(SqlString val)
{
    string[] splitStr = val.Value.Split(',');
    return splitStr;
}
private static void FillRow(Object obj, out SqlString str)
{
    object[] row = (object[])obj;
    str = (string)row[0];
}

However, executing it using

select * from dbo.SqlFunction1('1,2,3,4,5')

Returns the following error

Msg 6260, Level 16, State 1, Line 1
An error occurred while getting new row from user defined Table Valued Function : 
System.InvalidCastException: Unable to cast object of type 'System.String' to type 'System.Object[]'.
System.InvalidCastException: 
   at UserDefinedFunctions.FillRow(Object obj, SqlString& str)
.

Answer 1

You are taking a string reference and try to cast it to an object array, which causes the InvalidCastException.

Your SqlFunction1 method returns an array of strings, so the FillRow method will be called with a string reference. Cast the object reference back to string, and then create a SqlString value from it:

private static void FillRow(Object obj, out SqlString str) {
  string row = (string)obj;
  str = new SqlString(row);
}

Answer 2

I'm no C# expert, I'm a SQL dev, but this code has worked for me in the past. The method accepts a parameterised delimiter too. Sorry, I cannot directly answer your question. I can't even give you a source and credit the original author of the code - suffice to say it wasn't me.

using System;
using System.Data;
using System.Collections;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;

public partial class UserDefinedFunctions
{
    [SqlFunction(Name = "StringParserCLR",
    FillRowMethodName = "FillRow",
    TableDefinition = "string nvarchar(500)")]

    public static IEnumerable StringParserCLR(SqlString str, SqlChars delimiter)
    {
        if (delimiter.Length == 0)
        {
            return new string[1] { str.Value };
        }
        return str.Value.Split(delimiter[0]);
    }

    public static void FillRow(object row, out SqlString str)
    {
        str = new SqlString((string)row);
    }
};