Data type mismatch in criteria expression

Question

1.00/5 (1 vote)

See more:

I try Show Data in datagridview in C# Form AccessDatabase data show Correctly
but when i try filter data by LoanNumber This Error Show

An unhandled exception of type 'System.Data.OleDb.OleDbException' occurred in System.Data.dll

Additional information: Data type mismatch in criteria expression.

If i Delete this Statement from where "LoanNumber="+textBoxLoanNumber.Text+"
then Code Work Fine but in need show only Filter Data

What I have tried:

C#

private void loanDataLoad()
        {
            String connstring = ConfigurationManager.ConnectionStrings["FincorpData"].ConnectionString;
            OleDbConnection cnn = new OleDbConnection(connstring);
            OleDbDataAdapter adapter = new OleDbDataAdapter();
            string sql = "select InstallmentNumber, LoanNumber, InstallmentDate, LoanAmount, PaymentStatus from installment where LoanNumber="+textBoxLoanNumber.Text+"";
            DataSet ds = new DataSet();
            {
                   cnn.Open();
                   adapter = new OleDbDataAdapter(sql,cnn);
                   adapter.Fill(ds);
                   cnn.Close();
                   dataGridView1.DataSource = ds.Tables[0];
            }
        }

Posted 18-Mar-20 20:19pm

Amar chand123

Updated 18-Mar-20 20:54pm

KarstenK

v2

Add a Solution

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

OriginalGriff · Accepted Answer · 2020-03-18T20:55:00

Do not do it like that - and ignore KarstenK as well!
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.

So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?

C#

using (SqlConnection con = new SqlConnection(strConnect))
    {
    con.Open();
    using (SqlDataAdapter da = new SqlDataAdapter("SELECT MyColumn1, MyColumn2 FROM myTable WHERE mySearchColumn = @SEARCH", con))
        {
        da.SelectCommand.Parameters.AddWithValue("@SEARCH", myTextBox.Text);
        DataTable dt = new DataTable();
        da.Fill(dt);
        myDataGridView.DataSource = dt;
        }
    }