我有一个DataTable，我想在将它们添加到DataGridView之前做一些数学运算。第一个，我想找到我的DataTable的第三列的最大数量，第二个我想要将第三列中的所有值除以此最大数量。毕竟我想替换旧值而不是旧值。我的DataTable看起来像那样;
Column 1 Column 2 Column 3
---------------------------------------
a b 2000000
q r 250000
s t 185000
m w 400000
o p 750000
在操作之后，我的DataTable看起来应该是这样的;
Column 1 Column 2 Column 3
---------------------------------------
a b 1
q r 0.125
s t 0.0925
m w 0.0002
o p 0.375
这是我的代码;
connection.Open();
//Some insignificant operations here.
for (int q = 0; q < w.Length; q++)
{
for (int a = q + 1; a < w.Length; a++)
{
string query = ".....";
SqlDataAdapter myAdapter = new SqlDataAdapter(query, connection);
DataTable myTable = new DataTable();
myAdapter.Fill(myTable);
//I started here for finding maximum number in DataTable.
int[] myColumn = dt.AsEnumerable().Select(x => x.Field<int>("Column3")).ToArray();
int myMaximum = myColumn.Max();
//I don't know what should I do after that.
foreach (DataRow myRows in myTable.Rows)
{
//Some significant operations again...
dgv1.Rows.Add(...);
}
}
}
connection.Close();
放手一搏：
var max = myTable.Rows.Cast<DataRow>().Max(r => r.Field<double>("Column 3"));
foreach (var row in myTable.Rows.Cast<DataRow>())
{
row["Column 3"] = row.Field<double>("Column 3") / max;
}
可运行的测试代码：
var myTable = new DataTable();
myTable.Columns.Add("Column 3", typeof(double));
myTable.Rows.Add(20_00_000);
myTable.Rows.Add(250_000);
myTable.Rows.Add(185_000);
myTable.Rows.Add(400_000);
myTable.Rows.Add(750_000);
Console.WriteLine(String.Join(", ", myTable.Rows.Cast<DataRow>().Select(r => r.Field<double>("Column 3"))));
var max = myTable.Rows.Cast<DataRow>().Max(r => r.Field<double>("Column 3"));
foreach (var row in myTable.Rows.Cast<DataRow>())
{
row["Column 3"] = row.Field<double>("Column 3") / max;
}
Console.WriteLine(String.Join(", ", myTable.Rows.Cast<DataRow>().Select(r => r.Field<double>("Column 3"))));
这输出：
2000000, 250000, 185000, 400000, 750000 1, 0.125, 0.0925, 0.2, 0.375
更新基于“第3列”是int。
Console.WriteLine(String.Join(", ", myTable.Rows.Cast<DataRow>().Select(r => r.Field<int>("Column 3"))));
int max = myTable.Rows.Cast<DataRow>().Max(r => r.Field<int>("Column 3"));
double[] results = myTable.Rows.Cast<DataRow>().Select(r => (double)r.Field<int>("Column 3") / max).ToArray();
Console.WriteLine(String.Join(", ", results));
现在，当你建立你的results时，只需索引到DataGridView。
我建议摆脱DataTable并使用简单的c＃类。
DataTable是“重型”结构，它比你需要的更多，在大多数情况下你不需要它。
创建表示您的数据的类
public class Item
{
public string Column1 { get; set; }
public string Column2 { get; set; }
public int Column3 { get; set; }
}
加载数据
public List<Item> LoadData()
{
var query = "SELECT Column1, Column2, Column3 FROM Table";
using (var connection = new SqlConnection(connectionString))
using (var command = connection.CreateCommand())
{
command.CommandType = CommandType.Text;
command.CommandText = query;
using (var reader = command.ExecuteReader())
{
var data = new List<Item>();
while(reader.Read())
{
var item = new Item
{
Column1 = reader.GetString(0),
Column1 = reader.GetString(1),
Column1 = reader.GetInt32(2)
};
data.Add(item);
}
return data;
}
}
}
创建将代表计算数据的类
public class CalculatedItem
{
public string Column1 { get; }
public string Column2 { get; }
public decimal Calculated { get; }
public CalculatedItem(Item item, decimal maxValue)
{
Column1 = item.Column1;
Column2 = item.Column2;
Calculated = (decimal)item.Column3 / maxValue
}
}
用法
var data = LoadData();
var maxValue = data.Select(item => item.Column3).Max();
var calculatedData = data.Select(item => new CalculatedItem(item, maxValue)).ToList();
// Bind data to the DataGridView
DataGridView1.DataSource = calculatedDate;
您是否考虑过在现有表格中添加第4列？使列成为“表达式”列，按照您的描述进行数学运算，然后隐藏第三列？
这方面的一个例子如下......
DataTable GridTable;
public Form1() {
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e) {
GridTable = GetDataTable();
FillTable(GridTable);
AddExpressionColumn(GridTable);
dataGridView1.DataSource = GridTable;
dataGridView1.Columns["Column3"].Visible = false;
}
private DataTable GetDataTable() {
DataTable dt = new DataTable();
dt.Columns.Add("Column1", typeof(string));
dt.Columns.Add("Column2", typeof(string));
dt.Columns.Add("Column3", typeof(int));
return dt;
}
private void FillTable(DataTable dt) {
dt.Rows.Add("a", "b", 2000000);
dt.Rows.Add("q", "r", 250000);
dt.Rows.Add("s", "t", 185000);
dt.Rows.Add("m", "w", 400000);
dt.Rows.Add("o", "p", 750000);
}
private void AddExpressionColumn(DataTable dt) {
DataColumn expCol = new DataColumn("Result", typeof(decimal));
dt.Columns.Add(expCol);
string expressionString = "Column3 / " + GetMaxValue(dt).ToString();
expCol.Expression = expressionString;
}
private int GetMaxValue(DataTable dt) {
int max = (int)dt.Compute("Max(Column3)", "");
if (max == 0)
return 1;
return max;
}