String.format for a SQL query in C#

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Hi all,
can anyone give me a suggestion how to write a query containing join with the help of string.Format .I want to define the format of my sql query prehand as a readonly field.

Here is the query:

Select distinct sysI.rows AS Result , sysTab.NAME FROM sysindexes sysI
JOIN sys.Tables sysTab
ON sysI.ID = sysTab.OBJECT_ID
Where sysI.ID =  OBJECT_ID('TableName') AND sysI.indid < 2;

What I have tried:

I have tried writing the format as readonly field like following:

private readonly string STATEMENT_FORMAT = "SELECT {0}{1} FROM [dbo].[{2}]{3}{4}{5}{6}";

Posted 30-Jun-19 23:49pm

Member 10017141

Updated 1-Jul-19 4:25am

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Maciej Los 1-Jul-19 6:17am

Can you explain why are you trying to do that?

3 solutions

Solution 1

What you're doing is a bad idea, but if your question is how you use string.format then consult the documentation

String.Format Method (System) | Microsoft Docs[^]

Posted 30-Jun-19 23:54pm

F-ES Sitecore

Solution 4

Please read OriginalGriffs response regarding SQL Injection.

The proper way to place variable names into an SQL statement is via Parameters.

C#

string tsql = "Select distinct sysI.rows AS Result , sysTab.NAME FROM sysindexes sysI JOIN sys.Tables sysTab ON sysI.ID = sysTab.OBJECT_ID Where sysI.ID =  OBJECT_ID(@TableName) AND sysI.indid < 2";

string TableName = ""; // insert table name here

using (SqlConnection conn = new SqlConnection("connectionstring")) {
  SqlCommand cmd = new SqlCommand(tsql, conn);
  cmd.Parameters.Add("@TableName", TableName);
  conn.Open();


  // your sql data reader code


  conn.Close();
  conn.Dispose();
}

Reference: SqlParameter Class (System.Data.SqlClient) | Microsoft Docs[^]

Posted 1-Jul-19 4:26am

MadMyche

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OriginalGriff · Accepted Answer · 2019-07-01T00:45:00

What you are trying to do is probably a very bad idea: unless you are very, very careful it leaves you wide open to accidental or deliberate SQL Injection which can damage of destroy your database.

Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Always use Parameterized queries instead.

When you concatenate strings, you cause problems because SQL receives commands like:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'

The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;--'

Which SQL sees as three separate commands:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';

A perfectly valid SELECT

SQL

DROP TABLE MyTable;

A perfectly valid "delete the table" command

SQL

--'

And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.

Depending on how exactly you use this, you will put your DB at at least some degree of damage - if you or any other coder using this at a later date allows the user to enter data directly into any of those fields the risk grows to a near certainty of problems.

I would very strongly recommend that you scrap the whole idea!