error cannot convert from 'object' to 'string'

Question

I get some errors in my code below could any one help?

error cannot convert from 'object' to 'string' The best overloaded method match for 'System.IO.File.Exists(string)' has some invalid arguments

string theUserId = Session["UserID"].ToString();
OdbcConnection cn = new OdbcConnection("Driver={MySQL ODBC 3.51 Driver}; Server=localhost; Database=gymwebsite2; User=x; Password=x;");
cn.Open();

OdbcCommand sc = new OdbcCommand(string.Format("SELECT picturepath FROM Pictures WHERE UserID ='{0}'", theUserId), cn);
OdbcDataReader reader = sc.ExecuteReader();
while (reader.Read())
{
if (System.IO.File.Exists(reader[0]))
{  // error cannot convert from 'object' to 'string'
   // The best overloaded method match for 'System.IO.File.Exists(string)' has some invalid arguments
    System.IO.File.Delete(reader[0]);
}  // error cannot convert from 'object' to 'string'
   // The best overloaded method match for 'System.IO.File.Delete(string)' has some invalid arguments
}

How can this be fixed?

Careful... you've got a SQL injection vulnerability here.

p.campbell
– p.campbell

2011-03-25 22:32:38 +00:00
Commented Mar 25, 2011 at 22:32 — p.campbell
– p.campbell, Commented Mar 25, 2011 at 22:32
yup I know :) thanks tho

G Gr
– G Gr

2011-03-25 22:38:54 +00:00
Commented Mar 25, 2011 at 22:38 — G Gr
– G Gr, Commented Mar 25, 2011 at 22:38

Marc Gravell · Accepted Answer · 2011-03-25 22:28:06Z

11

Replace reader[0] with either:

reader.GetString(0)

or

Convert.ToString(reader[0])

(since reader[0] is for arbitrary data, so typed as object - but that method expects a string)

answered Mar 25, 2011 at 22:28

Marc Gravell

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Comments

Matt Greer · Accepted Answer · 2011-03-25 22:29:10Z

1

The quick solution is this:

// note addition of "as string"
if (System.IO.File.Exists(reader[0] as string))

However you should be sure that the element at that position really is a string.

answered Mar 25, 2011 at 22:29

Matt Greer

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2 Comments

Marc Gravell Over a year ago

Actually, I'd use (string)reader[0] if going this route; the exception message will be clearer if we get it wrong - cast vs null-arg)

Harry Steinhilber Over a year ago

See that too often. as should almost always be followed by a null check, never used directly.

Andrie · Accepted Answer · 2011-03-25 22:43:16Z

0

If reader[0] is indeed a string object, reader[0].ToString() will return the string value.

While debugging, you can check what type reader[0] by calling the get type method in the immediate window.

e.g. reader[0].GetType()

answered Mar 25, 2011 at 22:43

Andrie

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Comments

Tushar Gupta - curioustushar · Accepted Answer · 2014-03-30 13:22:37Z

0

OleDbDataAdapter da = new OleDbDataAdapter("select fact_code,fact_cost,fact_date from factor where fact_date between '" + int.Parse(comboBox2.SelectedItem )+ "/" + int.Parse(comboBox1.SelectedItem) + "/" + int.Parse(comboBox3.SelectedItem) + "'and '" + int.Parse(comboBox5.SelectedItem) + "/" + int.Parse(comboBox4.SelectedItem) + "/" + int.Parse(comboBox6.SelectedItem) + "'", con);
                DataSet dt = new DataSet();
                da.Fill(dt);
                dataGridView1.DataSource = dt.Tables[0];

edited Mar 30, 2014 at 13:22

Tushar Gupta - curioustushar

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answered Mar 30, 2014 at 13:00

user3428401

1

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