SQL command for access database select in c#

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for connecting a .mdb database from C#, how to pass a variable for selecting, e.g.:

for a string field called "a", if I directly pass a string to it, it is OK, e.g.

C#

OleDbCommand cmd = new OleDbCommand(@"SELECT * FROM mytable where a= 'hello' " , con);

but now I want to pass a string variable str_var to it, how to do?

the following one is wrong,

C#

OleDbCommand cmd = new OleDbCommand("SELECT * FROM mytable where a = " + str_var , con);

the following one is also not correct:

C#

OleDbCommand cmd = new OleDbCommand("SELECT * FROM mytable where a = @str_var "  , con);

what would be the correct one?

thanks!

Posted 21-Jul-12 9:41am

Seraph_summer

Updated 21-Jul-12 10:41am

Wonde Tadesse

v4

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abhinavvijay 21-Jul-12 15:54pm

when you use
OleDbCommand cmd = new OleDbCommand("SELECT * FROM mytable where a = " + str_var , con);
what error is showing?

Seraph_summer 21-Jul-12 16:02pm

with str_var="hello", if I run OleDbDataReader reader = cmd.ExecuteReader(); then reader is null.
but if simply put directly OleDbCommand cmd = new OleDbCommand("SELECT * FROM mytable where a = 'hello' ", con); it return correct value.

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**R. Giskard Reventlov** · Accepted Answer · 2012-07-21T09:55:00

Solution 1

OleDbCommand cmd = new OleDbCommand("SELECT * FROM mytable where a = '" + str_var + "'" , con);

I think that's what you mean.

Posted 21-Jul-12 9:55am

R. Giskard Reventlov

Comments

Seraph_summer 21-Jul-12 16:05pm

great! that is what I mean. thanks a lot! this waste me a lot of time!!
it seems here is different from SqlConnection, as for SQL connection, OleDbCommand cmd = new OleDbCommand("SELECT * FROM mytable where a = @str_var " , con); should work, right?

Seraph_summer 21-Jul-12 16:08pm

also, I am wondering why here so many quote? can you explain to me?
thanks!

R. Giskard Reventlov 21-Jul-12 17:07pm

Firstly, you should really use a stored procedure and pass any values as pasrameters.