why can´t I compare string from gridview to string in database

[BonaDrag]

I have an error I don't understand how to get rid of. I want to compare a string consisting of: ID + " " + date + " " + time + ":00" to a string in the database (data type = text).

Here's an example of what I fetch from my gridview:
1 + " " + 2010-07-07 + " " + 10:00 + ":00" (i.e. 1 2010-07-07 10:00:00)
and this is what I want to compare it to:
1 2010-07-07 10:00:00
The error message says "Incorrect syntax near '2010'." What did I miss? The values I get when I try to debug are the exakt same values that I want to compare.

Here's the code (some of it in swedish *sorry*, some c# as well as sql:

int möteID;   //=ID
        string datum; //=date
        string tid;   
        string starttid;  //=the time I'm using
        string sluttid;
        string tillfälleID; //=the string from the gridview

        StringBuilder str = new StringBuilder();
        int index = int.Parse(e.CommandArgument.ToString());
        möteID = Convert.ToInt32(GridViewFöreslagnaMöten.Rows[index].Cells[0].Text);
        datum = Convert.ToString(GridViewFöreslagnaMöten.Rows[index].Cells[2].Text); 
        tid = Convert.ToString(GridViewFöreslagnaMöten.Rows[index].Cells[3].Text);
        starttid = tid.Substring(1, 5);
        sluttid = tid.Substring(9, 5);
        tillfälleID = Convert.ToString(möteID + " " + datum + " " + starttid + ":00");

        SqlConnection conn = new SqlConnection(config);
        conn.Open();

        string sql = "SELECT medlemID FROM MedlemTillfalle WHERE MedlemTillfalle.tillfalleID = " + tillfälleID;

        SqlCommand comm = new SqlCommand(sql, conn);
        SqlDataReader dr = comm.ExecuteReader(); //Incorrect syntax near '2010'

...and I'm aware I'm not using parameters... I'll be getting there soon, still a newbie.

[BonaDrag]

Here's a possible explanation I found in another forum:
"You can't use text columns in an equal operation of a WHERE clause. If you are using SQL Express or SQL Server 2005, change your column type from text to either varchar(max) or nvarchar(max)".
To be continued...