"Cannot perform '=' operation on System.Int32 and System.String" 正在执行搜索

Question

正在尝试通过 DataList 进行搜索，参数是电影类型（通过数据库加载，因此没有 switch case）和名称

protected void ButtonFilter_Click(object sender, EventArgs e)
    {
        string filter = "";
        int selectedCount = 0;
        for (int i = 0; i < this.CheckBoxListGenres.Items.Count; i++)
            if (this.CheckBoxListGenres.Items[i].Selected)
                selectedCount++;
        if (selectedCount > 0)
        {
            filter = "GenreID=";
            int n = 0; //Used to determine to which genre the loop has arrived
            for (int i = 0; i < this.CheckBoxListGenres.Items.Count; i++)
            {
                if (this.CheckBoxListGenres.Items[i].Selected)
                {
                    if (n > 0 && n < selectedCount)
                        filter += " AND ";
                    filter+="'*"+this.CheckBoxListGenres.Items[i].Value.ToString()+"*'";
                    n++;

                }
            }

            if (this.TextBoxMovieName.Text!="")
                filter += " AND MovieName LIKE '*" + this.TextBoxMovieName.Text + "*'";
            DataTable dataTable = ((DataSet)Application["DataSetMovies"]).Tables[0];
            DataView dataView = new DataView(dataTable);
            filter = Convert.ToString(filter);
            dataView.RowFilter = filter; //!Getting the error here!
            this.DataListMovies.DataSource = dataView;
            this.DataListMovies.DataBind();
        }
    }

试过调试，字符串本身似乎没问题，所以我尝试在过滤器上使用 Convert.ToString() ，只是为了确定，但没关系。帮忙？

提前致谢

Answer 1

您的条件中的过滤器可能无效，因此请在 AND

的位置使用 OR

Use % , insted of * in LIKE Operator

I.E filter += " AND MovieName LIKE '%" + this.TextBoxMovieName.Text + "%'";

protected void ButtonFilter_Click(object sender, EventArgs e)
    {
        string filter = "";
        int selectedCount = 0;
        for (int i = 0; i < this.CheckBoxListGenres.Items.Count; i++)
            if (this.CheckBoxListGenres.Items[i].Selected)
                selectedCount++;
        if (selectedCount > 0)
        {
            filter = "GenreID=";
            int n = 0; //Used to determine to which genre the loop has arrived
            for (int i = 0; i < this.CheckBoxListGenres.Items.Count; i++)
            {
                if (this.CheckBoxListGenres.Items[i].Selected)
                {
                    if (n > 0 && n < selectedCount)
                        filter += " OR ";
                    filter+="'%"+this.CheckBoxListGenres.Items[i].Value.ToString()+"%'";
                    n++;

                }
            }

            if (this.TextBoxMovieName.Text!="")
                filter += " OR MovieName LIKE '%" + this.TextBoxMovieName.Text + "%'";
            DataTable dataTable = ((DataSet)Application["DataSetMovies"]).Tables[0];
            DataView dataView = new DataView(dataTable);
            filter = Convert.ToString(filter);
            dataView.RowFilter = filter;
            this.DataListMovies.DataSource = dataView;
            this.DataListMovies.DataBind();
        }
    }

Answer 2

这不是编译时错误这是运行时错误。

嗯，在你的数据库中，你正在应用过滤器的东西是 Int32 类型..

例如，如果你有类似 Num 的东西，它属于 Int32，但你做了如下的事情 :-

dv.RowFilter = "Num = '7097'" ////This will have error

它会抛出错误，因为它需要：-

dv.RowFilter = "Num = 7097" ////This is correct

所以在你的情况下你有 GenreID 它是 Int32 但在你的代码中你提供了一些字符串来反对它。

Answer 3

您的 GenreID 列可能是一个 INTEGER，您正在将它与 STRING 进行比较，如 '**' 中所示。在此示例中，我使用 IN 运算符一次列出所有值，它们之间没有 AND 运算符，这会导致逻辑错误，因为 none 项目将具有 GenreID=1 和 GenreID=2:

protected void ButtonFilter_Click(object sender, EventArgs e)
{
    string filter = "1=1";
    if (this.CheckBoxListGenres.Items.OfType<ListItem>().Any(i => i.Selected))
        filter += String.Format(" AND GenreID IN ({0})'",
            String.Join(",", this.CheckBoxListGenres.Items.OfType<ListItem>()
                .Where(i => i.Selected).Select(i => i.Value)));

    if (this.TextBoxMovieName.Text != "")
        filter += " AND MovieName LIKE '%" + this.TextBoxMovieName.Text + "%'";

    DataTable dataTable = ((DataSet)MediaTypeNames.Application["DataSetMovies"]).Tables[0];
    DataView dataView = new DataView(dataTable);
    dataView.RowFilter = filter;
    DataListMovies.DataSource = dataView;
    DataListMovies.DataBind();
}

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.net-3.5