Extracting a substring from a given string in textbox

Question

1.00/5 (1 vote)

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Hello,
I want to extract a substring from a string which the user enters into the textbox in C#. The substring I need would be in between the string entered.
For example,
if the user enters "select asd,fkdl from table",
I need "asd,fkdl" as my substring.

How do I do that Please help.

What I have tried:

C#

private void textBox1_TextChanged(object sender, EventArgs e)
        {
            string x = (sender as Control).Text;
            string temp;
            listBox1.BeginUpdate();
            string str = textBox1.Text.ToString();
            int p = str.IndexOf(' ');
            int len = str.Length;
            try
            {
                for (int i = 8; str[i] != ' '; i++)
                {
                    var substr = str.Substring(8,i+1);
                    temp = substr;
                    MessageBox.Show(temp,"Substring");
                }  
}
            finally
            {
                listBox1.EndUpdate();
            }

Posted 19-Jul-16 23:24pm

Ankush Soni

Updated 20-Jul-16 8:00am

CPallini

v2

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Comments

Leo Chapiro 20-Jul-16 5:32am

If the substring you are looking for is separated by blancs, you can use the Split methode of String-Class.

5 solutions

Solution 1

It is time to learn about Regular Expressions[^].

Posted 19-Jul-16 23:30pm

CPallini

Solution 5

You need to learn Regular Expressions (RegEx).
perlre - perldoc.perl.org[^]
Debuggex: Online visual regex tester. JavaScript, Python, and PCRE.[^]
.NET Regex Tester - Regex Storm[^]

Posted 20-Jul-16 8:00am

Patrice T

Solution 4

Obviously you do Need some SQL parsing. This solution is maybe overkill, on the other hand it will help you in case you go in future for more complex SQL statements.

With TSql110Parser you can easely let parse an SQL. You need to add the reference for Microsoft.SqlServer.TransactSql.ScriptDom, see also link at the end of this answer.

C#

private void buttonParseSQL_Click(object sender, EventArgs e)
{
    string sql = "SELECT a, b, c FROM tbl";

    // Parser
    IList<parseerror> errors;
    TSql110Parser parser = new TSql110Parser(true);
    var sqlFragment = parser.Parse(new System.IO.StringReader(sql), out errors);

    IList<tsqlparsertoken> tokenStream= sqlFragment.ScriptTokenStream;
    foreach (TSqlParserToken token in tokenStream)
    {
        // Do what you need with TSqlParserToken
        //         public int Column { get; set; }
        //         public int Line { get; set; }
        //         public int Offset { get; set; }
        //         public string Text { get; set; }
        //         public TSqlTokenType TokenType { get; set; }
        //         public bool IsKeyword();
    }
 }

Here you will find some usefull innformation: Removing Comments from SQL | Michael J. Swart[^]Hope it helps.

Posted 20-Jul-16 6:36am

User 11060979

Updated 20-Jul-16 6:55am

v3

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OriginalGriff · Accepted Answer · 2016-07-19T23:32:00

Solution 2

Use a regex:

C#

string input = "select asd,fkdl from table";
Match m = Regex.Match(input, @"(?<=select\s+).+?(?=\s+from)", RegexOptions.IgnoreCase);
if (m.Success)
    {
    string substr = m.Value;
    }

Posted 19-Jul-16 23:32pm

OriginalGriff

Comments

Ankush Soni 20-Jul-16 23:52pm

Thank you So Much. This worked. :)

OriginalGriff 21-Jul-16 3:33am

You're welcome!

Karthik_Mahalingam · Accepted Answer · 2016-07-20T00:11:00

Solution 3

without using Regex

C#

string input = "select asd,fkdl from table";
        int start = input.IndexOf("select")+6;
        var columns =  input.Substring(start, input.IndexOf("from") - start).Trim(); //"asd,fkdl"

Posted 20-Jul-16 0:11am

Karthik_Mahalingam

Comments

Ankush Soni 20-Jul-16 6:20am

Thank you so much. Just wanted to know one thing, do I still need to use the for loop?

Karthik_Mahalingam 20-Jul-16 6:25am

no need of any loop.

Ankush Soni 20-Jul-16 6:37am

Thank you.:)
But this worked for a specific case. the string input from the user is varying or we can say that the users enter his string in a textbox

Karthik_Mahalingam 20-Jul-16 6:55am

you have to analyse for multiple scenario and code based on that.

Ankush Soni 20-Jul-16 23:54pm

Thank you so much for the basic idea. Helped to develop the working code for other cases, without using regex. :)

Karthik_Mahalingam 21-Jul-16 0:47am

:)