parameter | Tidbytez

This is a simple tutorial on passing arguments or parameter values from command line to a console application written in C#. Using the example below you should be able to edit and expand on the logic to fit your own needs.

First you’ll need to create a new Visual Studio C# console application, to do so follow these steps:

To create and run a console application

Start Visual Studio.
On the menu bar, choose File, New, Project.
Expand Installed, expand Templates, expand Visual C#, and then choose Console Application.
In the Name box, specify a name for your project, and then choose the OK button.
If Program.cs isn’t open in the Code Editor, open the shortcut menu for Program.cs in Solution Explorer, and then choose View Code.
Replace the contents of Program.cs with the following code.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace TestArgsInput
{
    class Program
    {
        static void Main(string[] args)
        {
            if (args.Length == 0)
            {
				// Display message to user to provide parameters.
                System.Console.WriteLine("Please enter parameter values.");
                Console.Read();
            }
            else
            {
                // Loop through array to list args parameters.
                for (int i = 0; i < args.Length; i++)
                {
                    Console.Write(args[i] + Environment.NewLine);
                    
                }
                // Keep the console window open after the program has run.
                Console.Read();
            }
        }
    }
}

The Main method is the entry point of a C# application. When the application is started, the Main method is the first method that is invoked.

The parameter of the Main method is a String array that represents the command-line arguments. Usually you determine whether arguments exist by testing the Length property as in the example above.

When run the example above will list out the parameters you have provided to the command window. The delimiter for command line separating arguments or parameter values is a single space. For example the following would be interpreted as two arguments or parameter values:

“This is parameter 1” “This is parameter 2”

If the arguments were not enclosed by double quotes each word would be considered an argument.

To pass arguments to the console application when testing the application logic the arguments can be written into the debug section of the project properties as shown below.

TestArgs

So if the app is run with the command line arguments provided as above in the image the command window will list:

Parameter 1

Parameter 2

If you would like to know how to create a console application in Visual Studio that won’t open a command window when it runs see this tutorial link.

If you would like to know how to create a csv file with C# see this tutorial link.

When you allow for multiple field values to be selected in a SSRS report there needs to be additional logic added to the back end to deal with this.

This is best explained with an example scenario.

I have a table called Ireland with two columns, ID_Column and County. You can use the script below to create and populate this table. Run the query below to follow the working example.

CREATE DATABASE [TEST_DB];

USE [TEST_DB];
GO

/****** Object:  Table [dbo].[Ireland]    Script Date: 07/15/2015 10:49:49 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

SET ANSI_PADDING ON
GO

CREATE TABLE [dbo].[Ireland] (
	[ID_Column] [int] IDENTITY(1, 1) NOT NULL
	,[County] [varchar](9) NULL
	,PRIMARY KEY CLUSTERED ([ID_Column] ASC) WITH (
		PAD_INDEX = OFF
		,STATISTICS_NORECOMPUTE = OFF
		,IGNORE_DUP_KEY = OFF
		,ALLOW_ROW_LOCKS = ON
		,ALLOW_PAGE_LOCKS = ON
		) ON [PRIMARY]
	) ON [PRIMARY]
GO

SET ANSI_PADDING OFF
GO

SET IDENTITY_INSERT [dbo].[Ireland] ON

INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (1, N'Antrim')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (2, N'Armagh')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (3, N'Carlow')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (4, N'Cavan')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (5, N'Clare')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (6, N'Cork')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (7, N'Derry')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (8, N'Donegal')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (9, N'Down')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (10, N'Dublin')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (11, N'Fermanagh')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (12, N'Galway')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (13, N'Kerry')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (14, N'Kildare')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (15, N'Kilkenny')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (16, N'Laois')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (17, N'Leitrim')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (18, N'Limerick')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (19, N'Longford')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (20, N'Louth')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (21, N'Mayo')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (22, N'Meath')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (23, N'Monaghan')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (24, N'Offaly')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (25, N'Roscommon')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (26, N'Sligo')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (27, N'Tipperary')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (28, N'Tyrone')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (29, N'Waterford')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (30, N'Westmeath')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (31, N'Wexford')
INSERT [dbo].[Ireland] ([ID_Column], [County]) VALUES (32, N'Wicklow')
SET IDENTITY_INSERT [dbo].[Ireland] OFF

If I wanted to allow a user to select every county from the Ireland table in an SSRS report I would create a stored procedure that simply executes the following query.

SELECT * FROM Ireland

However an SSRS report which allows users to choose counties in Ireland like below means that a WHERE clause needs to be introduced and be able to respond to the field values selected.

But the issue is that the SSRS report will pass the multi-valued parameter as a string with the values separated by a comma.

So instead of receiving the required: ‘Antrim’, ‘Armagh’, ‘Carlow’, ‘Cavan’ etc. for use in the WHERE clause.

SQL Server is passed: ‘Antrim, Armagh, Carlow, Cavan’ etc. which cannot be used.

So the first additional logic and code to be added to the back end to deal with the multi-value parameter is a User Defined Function (UDF) which splits the parameter. The following function and quotations are taken from the 4guysfromrolla website.

Function Scope:

“There are generally two parameters to a split function: the list to split and the character(s) to split on, the delimiter. In the following function we begin by declaring our input variables – @List, the list to split, and @SplitOn, the delimiter(s) to split on. The return value of this UDF is a table with two fields: Id, an identity column, and Value, an nvarchar(100) column.”

Function Logic:

“The main body of the function simply loops through the string finding the first occurrence of the delimiter on each pass. Once the delimiter has been found, the string is broken into two pieces. The first piece is inserted into the result table while the second piece replaces the original list. The loop continues until no more occurrences of the delimiter are found. Lastly, the remainder of the list is added to the result table. Return the table and you have a split function.”

Run the query below to follow the working example.

USE [TEST_DB];
GO

CREATE FUNCTION [dbo].[Split] (
	@List NVARCHAR(2000)
	,@SplitOn NVARCHAR(5)
	)
RETURNS @RtnValue TABLE (
	Id INT identity(1, 1)
	,Value NVARCHAR(100)
	)
AS
BEGIN
	WHILE (Charindex(@SplitOn, @List) > 0)
	BEGIN
		INSERT INTO @RtnValue (value)
		SELECT Value = ltrim(rtrim(Substring(@List, 1, Charindex(@SplitOn, @List) - 1)))

		SET @List = Substring(@List, Charindex(@SplitOn, @List) + len(@SplitOn), len(@List))
	END

	INSERT INTO @RtnValue (Value)
	SELECT Value = ltrim(rtrim(@List))

	RETURN
END

(For a line by line break down of the function please see the webpage.)

Now that the split function exits within the database it is now possible to use a Stored Procedure to SELECT from the Ireland table pulling back specific counties by way of a WHERE clause.

Run the query below to follow the working example.

USE Test_DB;
GO

IF OBJECT_ID('[GetCounties]') IS NULL
	EXEC ('CREATE PROCEDURE dbo.[GetCounties] AS SELECT 1')
GO

ALTER PROCEDURE [dbo].[GetCounties] @County VARCHAR(MAX)
AS
	/*

NAME OF SP: GetCounties
Author:		Bloggins86
Date:		15/07/2015
Purpose:	Test multi-parameter select

*/
	------------------------------------------------------
	------------------------------------------------------
	--INSERT STORED PROCEDURE LOGIC HERE
	SELECT *
	FROM Ireland
	WHERE County IN (SELECT Value FROM dbo.Split(@County, ','))

	------------------------------------------------------
	------------------------------------------------------

Now that the populated table, split function and county select SP exists run the query below passing a string with multiple counties to return Dublin, Meath and Cork from the Ireland Table.

EXEC dbo.[GetCounties] 'Dublin, Meath, Cork'

You should now have returned the table with Dublin, Meath and Cork as separate row entries.

And that’s it, thanks for reading.

Tidbytez

Delivering Bite-Sized Tech Knowledge

Tag Archives: parameter

How to pass arguments from command line to a console application written in C#

To create and run a console application

How to pass a multi-value parameter to a stored procedure from a SSRS Report

To create and run a console application

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