Show tables using entity framework

Question

I am trying to show all the data of t1 table in a gridview using Entity Framework but I am getting an error

LINQ to Entities does not recognize the method 'Int32 ToInt32(System.String)' method, and this method cannot be translated into a store expression.

This is my code:

protected void Button2_Click(object sender, EventArgs e)
{
    var v = (from obj in de.t1
             where obj.Id == Convert.ToInt32(TextBox5.Text)
             select obj).ToList();
    GridView1.DataSource = v;
    GridView1.DataBind();
}

Maybe read the error message and try to overcome it. It clearly says that using the method ToInt32 isnt allowed so dont use it inside the query convert the string to int outside of the linq... — Rand Random
– Rand Random, Commented Jun 30, 2014 at 18:32

Yurii · Accepted Answer · 2014-06-30 18:31:56Z

3

Entity Framework is trying to execute Convert.ToInt32(TextBox5.Text) on the SQL side, which it obviously cannot do.
So, introduce a temporary variable to store the result of conversion:

var tempId = Convert.ToInt32(TextBox5.Text);

Then pass it to the where clause:

...
where obj.Id == tempId
...

answered Jun 30, 2014 at 18:31

Yurii

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Comments

entropic · Accepted Answer · 2014-06-30 18:32:31Z

0

The problem you are running into is the fact that the entity framework doesn't know how to translate Convert.ToInt32 into a valid SQL expression. Simply cast the textbox value to an integer before you query, and things should be fine.

protected void Button2_Click(object sender, EventArgs e)
{
    int id = Convert.ToInt32(TextBox5.Text);
    var v = (from obj in de.t1
             where obj.Id == id
             select obj).ToList();
    GridView1.DataSource = v;
    GridView1.DataBind();
}

answered Jun 30, 2014 at 18:32

entropic

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Comments

Edminsson · Accepted Answer · 2014-06-30 18:32:58Z

0

protected void Button2_Click(object sender, EventArgs e)
{
    var objId = Convert.ToInt32(TextBox5.Text);
    var v = (from obj in de.t1
            where obj.Id == objId
            select obj).ToList();
    GridView1.DataSource = v;
    GridView1.DataBind();
}

answered Jun 30, 2014 at 18:32

Edminsson

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1 Comment

Alexander Over a year ago

Code only answers, which may well be a workable solution, are usually improved by some explanation. Please consider commenting or explaining how your suggested code works.

shredding · Accepted Answer · 2014-06-30 18:33:36Z

0

    protected void Button2_Click(object sender, EventArgs e)
        {
            var id = Convert.ToInt32(TextBox5.Text);
            var v = (from obj in de.t1
                    where obj.Id == id
                    select obj).ToList();
            GridView1.DataSource = v;
            GridView1.DataBind();
        }

edited Jun 30, 2014 at 18:33

answered Jun 30, 2014 at 18:31

shredding

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